Sync with Tramp 2.4.5-pre

* doc/misc/tramp.texi: Adapt Tramp and Emacs version numbers.
(Remote processes): Describe `process-file-return-signal-string'
and $INSIDE_EMACS.
(Frequently Asked Questions): Mention Emacs 28.
Describe `tramp-smb-options'.

* doc/misc/trampver.texi: Change version to "2.4.5-pre".

* lisp/net/tramp-adb.el (process-file-return-signal-string): Declare.
(tramp-adb-handle-write-region): Flush the cache after the file
has been written.
(tramp-adb-handle-set-file-modes, tramp-adb-handle-set-file-times):
Add optional _FLAG.
(tramp-adb-handle-copy-file, tramp-adb-handle-rename-file)
(tramp-adb-handle-process-file): Use `tramp-file-local-name'.
(tramp-adb-get-signal-strings): New defun.
(tramp-adb-handle-process-file): Use it.
(tramp-adb-handle-make-process): Implement `stderr'.  Use
`insert-file-contents-literally'.
(tramp-adb-send-command-and-check): Add optional argument
EXIT-STATUS.
(tramp-adb-handle-process-file): Use it.

* lisp/net/tramp-archive.el (tramp-archive-file-name-handler):
Increase `max-specpdl-size' temporarily.

* lisp/net/tramp-cache.el (top):
Use `insert-file-contents-literally'.

* lisp/net/tramp-cmds.el (tramp-rename-files):
Use `tramp-file-local-name'.

* lisp/net/tramp-gvfs.el (tramp-gvfs-enabled): Prevent crash for
older Emacsen.
(top): Adapt `tramp-gvfs-unload-hook'.
(tramp-gvfs-handle-file-system-info): Fix error.
(tramp-gvfs-handle-set-file-modes, tramp-gvfs-handle-set-file-times):
Add optional _FLAG.

* lisp/net/tramp-rclone.el (tramp-rclone-flush-directory-cache):
Fix a problem with older Emacsen.

* lisp/net/tramp-sh.el (process-file-return-signal-string): Declare.
(tramp-sh-extra-args): Add "-noediting" as bash arg.
(tramp-hexdump-encode, tramp-hexdump-awk-encode)
(tramp-od-encode, tramp-od-awk-encode): New defconst.
(tramp-awk-encode, tramp-awk-decode): Adapt.
(tramp-awk-coding-test): Remove.
(tramp-remote-coding-commands): Add hexdump/awk encoding.  (Bug#35639)
(tramp-find-inline-encoding): Adapt handling of awk, hexdump and od.
(tramp-get-remote-busybox, tramp-get-remote-awk)
(tramp-get-remote-hexdump, tramp-get-remote-od): New defuns.
(tramp-sh-handle-make-symbolic-link):
(tramp-do-copy-or-rename-file-directly)
(tramp-sh-handle-process-file, tramp-set-remote-path)
(tramp-find-inline-encoding, tramp-get-remote-touch):
Use `tramp-file-local-name'.
(tramp-do-file-attributes-with-stat): Simplify shell command.
Suppress errors (interpret as nil).
(tramp-sh-handle-set-file-modes, tramp-sh-handle-set-file-times):
Add optional _FLAG.
(tramp-sh-handle-make-process): Do not visit with
`insert-file-contents'.  Delete tmp file only if exists.  Support
`stderr' as file name.  Delete temporary stderr file.  Flush
connection properties in time.
(tramp-sh-get-signal-strings): New defun.
(tramp-sh-handle-process-file): Use it.
(tramp-sh-handle-write-region): Copy to temp file only if FILENAME
exists.  (Bug#40156)
(tramp-set-remote-path): Send the command in several chunks if it
is too large.  (Bug#42538)
(tramp-open-connection-setup-interactive-shell): Move up "set +o
vi +o emacs" command.   (Bug#39399)
(tramp-send-command-and-read): Suppress `signal-hook-function'
when reading expression.
(tramp-send-command-and-check): Add optional argument EXIT-STATUS.
(tramp-sh-handle-process-file): Use it.  (Bug#41099)

* lisp/net/tramp-smb.el (tramp-smb-conf): Fix docstring.
(tramp-smb-options): New defcustom.
(tramp-smb-handle-copy-directory, tramp-smb-handle-file-acl)
(tramp-smb-handle-set-file-acl, tramp-smb-maybe-open-connection):
Use it.
(tramp-smb-errors): Add "NT_STATUS_INVALID_PARAMETER".
(tramp-smb-handle-make-symbolic-link)
(tramp-smb-handle-process-file): Use `tramp-file-local-name'.

* lisp/net/tramp-sudoedit.el (tramp-sudoedit-do-copy-or-rename-file):
(tramp-sudoedit-handle-set-file-uid-gid):
Use `tramp-unquote-file-local-name'.
(tramp-sudoedit-handle-make-symbolic-link):
Use `tramp-file-local-name'.
(tramp-sudoedit-handle-file-system-info): Fix a scoping error.
(tramp-sudoedit-handle-set-file-modes):
(tramp-sudoedit-handle-set-file-times): Add optional _FLAG.

* lisp/net/tramp.el: Bump version to 2.4.5-pre.
(tramp-file-local-name, tramp-unquote-file-local-name): New defuns.
(tramp-set-connection-local-variables-for-buffer)
(tramp-equal-remote, tramp-handle-make-auto-save-file-name):
Use `tramp-tramp-file-p'.
(tramp-parse-file): Use `insert-file-contents-literally'.
(tramp-handle-file-modes, tramp-handle-file-times):
Add optional _FLAG.
(tramp-handle-shell-command): Fix `window-start' in output buffer.
(Bug#39171)
Handle `shell-command-dont-erase-buffer'.  (Bug#39067)
Reorganize error-buffer handling.  Set `default-directory'.
(Bug#39253)
(tramp-handle-shell-command, tramp-handle-start-file-process):
Implement asynchronous `error-buffer'.
(tramp-action-process-alive): Read pending output.
(tramp-read-passwd): Use `tramp-compat-temporary-file-directory'.
(Bug#39389, Bug#39489)
(tramp-interrupt-process): Improve command.

* lisp/net/trampver.el: Change version to "2.4.5-pre".
(tramp-repository-branch, tramp-repository-version):
Bind `debug-on-error' to nil.

* test/lisp/net/tramp-tests.el (tramp-get-remote-gid)
(process-file-return-signal-string)
(shell-command-dont-erase-buffer): Declare.
(tramp-test10-write-region, tramp-test28-process-file)
(tramp-test29-start-file-process, tramp-test30-make-process)
(tramp-test31-interrupt-process, tramp-test32-shell-command):
Extend test.
(tramp-test10-write-region, tramp-test21-file-links): Use function
symbols.
(tramp-test18-file-attributes): Check `file-ownership-preserved-p'
only if possible.
(tramp--test-async-shell-command): New defun.
(tramp--test-shell-command-to-string-asynchronously): Use it.
(tramp-test32-shell-command-dont-erase-buffer): New test.

15 files changed, 1103 insertions, 416 deletions

diff --git a/doc/misc/tramp.texi b/doc/misc/tramp.texi
index c68b9aad528..97a26421f2f 100644
--- a/doc/misc/tramp.texi
+++ b/doc/misc/tramp.texi
@@ -318,14 +318,14 @@ behind the scenes when you open a file with @value{tramp}.
 @uref{https://ftp.gnu.org/gnu/tramp/}.  The version number of
 @value{tramp} can be obtained by the variable @code{tramp-version}.
 For released @value{tramp} versions, this is a three-number string
-like ``2.4.2''.
+like ``2.4.3''.
 
 A @value{tramp} release, which is packaged with Emacs, could differ
 slightly from the corresponding standalone release.  This is because
 it isn't always possible to synchronize release dates between Emacs
 and @value{tramp}.  Such version numbers have the Emacs version number
-as suffix, like ``2.3.5.26.3''.  This means @value{tramp} 2.3.5 as
-integrated in Emacs 26.3.  A complete list of @value{tramp} versions
+as suffix, like ``2.4.3.27.1''.  This means @value{tramp} 2.4.3 as
+integrated in Emacs 27.1.  A complete list of @value{tramp} versions
 packaged with Emacs can be retrieved by
 
 @vindex customize-package-emacs-version-alist
@@ -337,12 +337,12 @@ packaged with Emacs can be retrieved by
 ELPA} package.  Besides the standalone releases, further minor version
 of @value{tramp} will appear on GNU ELPA, until the next @value{tramp}
 release appears.  These minor versions have a four-number string, like
-``2.4.2.1''.
+``2.4.3.1''.
 
 @value{tramp} development versions are available on Git servers.
 Development versions contain new and incomplete features.  The
 development version of @value{tramp} is always the version number of
-the next release, plus the suffix ``-pre'', like ``2.4.3-pre''.
+the next release, plus the suffix ``-pre'', like ``2.4.4-pre''.
 
 One way to obtain @value{tramp} from Git server is to visit the
 Savannah project page at the following URL and then clicking on the
@@ -2299,7 +2299,7 @@ string of that environment variable looks always like
 @example
 @group
 echo $INSIDE_EMACS
-@result{} 26.2,tramp:2.3.4
+@result{} 27.1,tramp:2.4.3
 @end group
 @end example
 
@@ -3034,6 +3034,17 @@ host when the variable @code{default-directory} is remote:
 @end group
 @end lisp
 
+@vindex process-file-return-signal-string
+@code{process-file} shall return either the exit code of the process,
+or a string describing the signal, when the process has been
+interrupted.  Since it cannot be determined reliably whether a remote
+process has been interrupted, @code{process-file} returns always the
+exit code.  When the user option
+@code{process-file-return-signal-string} is non-nil,
+@code{process-file} regards all exit codes greater than 128 as an
+indication that the process has been interrupted, and returns a
+respective string.
+
 Remote processes do not apply to @acronym{GVFS} (see @ref{GVFS-based
 methods}) because the remote file system is mounted on the local host
 and @value{tramp} just accesses by changing the
@@ -3041,9 +3052,17 @@ and @value{tramp} just accesses by changing the
 
 @value{tramp} starts a remote process when a command is executed in a
 remote file or directory buffer.  As of now, these packages have been
-integrated to work with @value{tramp}: @file{compile.el} (commands
-like @code{compile} and @code{grep}) and @file{gud.el} (@code{gdb} or
-@code{perldb}).
+integrated to work with @value{tramp}: @file{shell.el},
+@file{eshell.el}, @file{compile.el} (commands like @code{compile} and
+@code{grep}) and @file{gud.el} (@code{gdb} or @code{perldb}).
+
+@vindex INSIDE_EMACS@r{, environment variable}
+@value{tramp} always modifies the @env{INSIDE_EMACS} environment
+variable for remote processes.  Per default, this environment variable
+shows the Emacs version.  @value{tramp} adds its own version string,
+so it looks like @samp{27.1,tramp:2.4.3.1}.  However, other packages
+might also add their name to this environment variable, like
+@samp{27.1,comint,tramp:2.4.3.1}.
 
 For @value{tramp} to find the command on the remote, it must be
 accessible through the default search path as setup by @value{tramp}
@@ -3238,10 +3257,10 @@ variables.
 @vindex async-shell-command-width
 @vindex COLUMNS@r{, environment variable}
 If Emacs supports the variable @code{async-shell-command-width} (since
-Emacs 27.1), @value{tramp} cares about its value for asynchronous
-shell commands.  It specifies the number of display columns for
-command output.  For synchronous shell commands, a similar effect can
-be achieved by adding the environment variable @env{COLUMNS} to
+Emacs 27), @value{tramp} cares about its value for asynchronous shell
+commands.  It specifies the number of display columns for command
+output.  For synchronous shell commands, a similar effect can be
+achieved by adding the environment variable @env{COLUMNS} to
 @code{tramp-remote-process-environment}.
 
 
@@ -3725,7 +3744,7 @@ row are possible, like @file{/path/to/dir/file.tar.gz.uu/dir/file}.
 
 @vindex tramp-archive-all-gvfs-methods
 An archive file name could be a remote file name, as in
-@file{/ftp:anonymous@@ftp.gnu.org:/gnu/tramp/tramp-2.3.2.tar.gz/INSTALL}.
+@file{/ftp:anonymous@@ftp.gnu.org:/gnu/tramp/tramp-2.4.3.tar.gz/INSTALL}.
 Since all file operations are mapped internally to @acronym{GVFS}
 operations, remote file names supported by @code{tramp-gvfs} perform
 better, because no local copy of the file archive must be downloaded
@@ -3736,7 +3755,7 @@ the similar @samp{/scp:user@@host:...}.  See the constant
 
 If @code{url-handler-mode} is enabled, archives could be visited via
 URLs, like
-@file{https://ftp.gnu.org/gnu/tramp/tramp-2.3.2.tar.gz/INSTALL}.  This
+@file{https://ftp.gnu.org/gnu/tramp/tramp-2.4.3.tar.gz/INSTALL}.  This
 allows complex file operations like
 
 @lisp
@@ -3744,8 +3763,8 @@ allows complex file operations like
 (progn
   (url-handler-mode 1)
   (ediff-directories
-   "https://ftp.gnu.org/gnu/tramp/tramp-2.3.1.tar.gz/tramp-2.3.1"
-   "https://ftp.gnu.org/gnu/tramp/tramp-2.3.2.tar.gz/tramp-2.3.2" ""))
+   "https://ftp.gnu.org/gnu/tramp/tramp-2.4.2.tar.gz/tramp-2.4.2"
+   "https://ftp.gnu.org/gnu/tramp/tramp-2.4.3.tar.gz/tramp-2.4.3" ""))
 @end group
 @end lisp
 
@@ -3860,8 +3879,8 @@ Where is the latest @value{tramp}?
 @item
 Which systems does it work on?
 
-The package works successfully on Emacs 24, Emacs 25, Emacs 26, and
-Emacs 27.
+The package works successfully on Emacs 24, Emacs 25, Emacs 26, Emacs
+27, and Emacs 28.
 
 While Unix and Unix-like systems are the primary remote targets,
 @value{tramp} has equal success connecting to other platforms, such as
@@ -4128,6 +4147,23 @@ your proxy host.
 
 
 @item
+@value{tramp} does not connect to Samba or MS Windows hosts running
+SMB1 connection protocol.
+
+@vindex tramp-smb-options
+Recent versions of @command{smbclient} do not support old connection
+protocols by default.  In order to connect to such a host, add a
+respective option:
+
+@lisp
+(add-to-list 'tramp-smb-options "client min protocol=NT1")
+@end lisp
+
+@strong{Note} that using a deprecated connection protocol raises
+security problems, you should do it only if absolutely necessary.
+
+
+@item
 File name completion does not work with @value{tramp}
 
 @acronym{ANSI} escape sequences from the remote shell may cause errors
diff --git a/doc/misc/trampver.texi b/doc/misc/trampver.texi
index 478ec7037a8..cc3c768fe6e 100644
--- a/doc/misc/trampver.texi
+++ b/doc/misc/trampver.texi
@@ -8,7 +8,7 @@
 @c In the Tramp GIT, the version numbers are auto-frobbed from
 @c tramp.el, and the bug report address is auto-frobbed from
 @c configure.ac.
-@set trampver 2.4.3.27.1
+@set trampver 2.4.5-pre
 @set tramp-bug-report-address tramp-devel@@gnu.org
 @set emacsver 24.4
 
diff --git a/lisp/net/tramp-adb.el b/lisp/net/tramp-adb.el
index 5cfcb81708f..0efe055b084 100644
--- a/lisp/net/tramp-adb.el
+++ b/lisp/net/tramp-adb.el
@@ -35,6 +35,8 @@
 
 (require 'tramp)
 
+(defvar process-file-return-signal-string)
+
 ;;;###tramp-autoload
 (defcustom tramp-adb-program "adb"
   "Name of the Android Debug Bridge program."
@@ -631,9 +633,6 @@ But handle the case, if the \"test\" command is not available."
                      (format "File %s exists; overwrite anyway? " filename)))))
       (tramp-error v 'file-already-exists filename))
 
-    ;; We must also flush the cache of the directory, because
-    ;; `file-attributes' reads the values from there.
-    (tramp-flush-file-properties v localname)
     (let* ((curbuf (current-buffer))
            (tmpfile (tramp-compat-make-temp-file filename)))
       (when (and append (file-exists-p filename))
@@ -650,6 +649,10 @@ But handle the case, if the \"test\" command is not available."
               (tramp-error v 'file-error "Cannot write: `%s'" filename))
           (delete-file tmpfile)))
 
+      ;; We must also flush the cache of the directory, because
+      ;; `file-attributes' reads the values from there.
+      (tramp-flush-file-properties v localname)
+
       (unless (equal curbuf (current-buffer))
         (tramp-error
          v 'file-error
@@ -667,13 +670,13 @@ But handle the case, if the \"test\" command is not available."
         (tramp-message v 0 "Wrote %s" filename))
       (run-hooks 'tramp-handle-write-region-hook))))
 
-(defun tramp-adb-handle-set-file-modes (filename mode)
+(defun tramp-adb-handle-set-file-modes (filename mode &optional _flag)
   "Like `set-file-modes' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (tramp-flush-file-properties v localname)
     (tramp-adb-send-command-and-check v (format "chmod %o %s" mode localname))))
 
-(defun tramp-adb-handle-set-file-times (filename &optional time)
+(defun tramp-adb-handle-set-file-times (filename &optional time _flag)
   "Like `set-file-times' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (tramp-flush-file-properties v localname)
@@ -725,8 +728,8 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
         (with-tramp-progress-reporter
             v 0 (format "Copying %s to %s" filename newname)
           (if (and t1 t2 (tramp-equal-remote filename newname))
-              (let ((l1 (tramp-compat-file-local-name filename))
-                    (l2 (tramp-compat-file-local-name newname)))
+              (let ((l1 (tramp-file-local-name filename))
+                    (l2 (tramp-file-local-name newname)))
                 ;; We must also flush the cache of the directory,
                 ;; because `file-attributes' reads the values from
                 ;; there.
@@ -809,8 +812,8 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
           (if (and t1 t2
                    (tramp-equal-remote filename newname)
                    (not (file-directory-p filename)))
-              (let ((l1 (tramp-compat-file-local-name filename))
-                    (l2 (tramp-compat-file-local-name newname)))
+              (let ((l1 (tramp-file-local-name filename))
+                    (l2 (tramp-file-local-name newname)))
                 ;; We must also flush the cache of the directory, because
                 ;; `file-attributes' reads the values from there.
                 (tramp-flush-file-properties v l1)
@@ -828,6 +831,33 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
              filename newname ok-if-already-exists 'keep-time 'preserve-uid-gid)
             (delete-file filename)))))))
 
+(defun tramp-adb-get-signal-strings (vec)
+  "Strings to return by `process-file' in case of signals."
+  (with-tramp-connection-property vec "signal-strings"
+    (let ((default-directory (tramp-make-tramp-file-name vec 'localname))
+          ;; `shell-file-name' and `shell-command-switch' are needed
+          ;; for Emacs < 27.1, which doesn't support connection-local
+          ;; variables in `shell-command'.
+          (shell-file-name "/system/bin/sh")
+          (shell-command-switch "-c")
+          process-file-return-signal-string signals result)
+      (dotimes (i 128) (push (format "Signal %d" i) result))
+      (setq result (reverse result)
+            signals (split-string
+                     (shell-command-to-string "COLUMNS=40 kill -l") "\n" 'omit))
+      (setcar result 0)
+      (dolist (line signals)
+        (when (string-match
+               (concat
+                "^[[:space:]]*\\([[:digit:]]+\\)"
+                "[[:space:]]+\\S-+[[:space:]]+"
+                "\\([[:alpha:]].*\\)$")
+               line)
+          (setcar
+           (nthcdr (string-to-number (match-string 1 line)) result)
+           (match-string 2 line))))
+      result)))
+
 (defun tramp-adb-handle-process-file
   (program &optional infile destination display &rest args)
   "Like `process-file' for Tramp files."
@@ -846,7 +876,7 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
         (setq infile (expand-file-name infile))
         (if (tramp-equal-remote default-directory infile)
             ;; INFILE is on the same remote host.
-            (setq input (with-parsed-tramp-file-name infile nil localname))
+            (setq input (tramp-file-local-name infile))
           ;; INFILE must be copied to remote host.
           (setq input (tramp-make-tramp-temp-file v)
                 tmpinput (tramp-make-tramp-file-name v input))
@@ -877,8 +907,7 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
           (setcar (cdr destination) (expand-file-name (cadr destination)))
           (if (tramp-equal-remote default-directory (cadr destination))
               ;; stderr is on the same remote host.
-              (setq stderr (with-parsed-tramp-file-name
-                               (cadr destination) nil localname))
+              (setq stderr (tramp-file-local-name (cadr destination)))
             ;; stderr must be copied to remote host.  The temporary
             ;; file must be deleted after execution.
             (setq stderr (tramp-make-tramp-temp-file v)
@@ -895,14 +924,13 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
       ;; it.  Call it in a subshell, in order to preserve working
       ;; directory.
       (condition-case nil
-          (progn
-            (setq ret
-                  (if (tramp-adb-send-command-and-check
-                       v
-                       (format "(cd %s; %s)"
-                               (tramp-shell-quote-argument localname) command))
-                      ;; Set return status accordingly.
-                      0 1))
+          (unwind-protect
+              (setq ret (tramp-adb-send-command-and-check
+                         v (format
+                            "(cd %s; %s)"
+                            (tramp-shell-quote-argument localname) command)
+                         t))
+            (unless (natnump ret) (setq ret 1))
             ;; We should add the output anyway.
             (when outbuf
               (with-current-buffer outbuf
@@ -918,6 +946,12 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
          (kill-buffer (tramp-get-connection-buffer v))
          (setq ret 1)))
 
+      ;; Handle signals.  `process-file-return-signal-string' exists
+      ;; since Emacs 28.1.
+      (when (and (bound-and-true-p process-file-return-signal-string)
+                 (natnump ret) (> ret 128))
+        (setq ret (nth (- ret 128) (tramp-adb-get-signal-strings v))))
+
       ;; Provide error file.
       (when tmpstderr (rename-file tmpstderr (cadr destination) t))
 
@@ -936,6 +970,8 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
 ;; We use BUFFER also as connection buffer during setup.  Because of
 ;; this, its original contents must be saved, and restored once
 ;; connection has been setup.
+;; The complete STDERR buffer is available only when the process has
+;; terminated.
 (defun tramp-adb-handle-make-process (&rest args)
   "Like `make-process' for Tramp files."
   (when args
@@ -969,17 +1005,29 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
           (signal 'wrong-type-argument (list #'functionp sentinel)))
         (unless (or (null stderr) (bufferp stderr) (stringp stderr))
           (signal 'wrong-type-argument (list #'stringp stderr)))
+        (when (and (stringp stderr) (tramp-tramp-file-p stderr)
+                   (not (tramp-equal-remote default-directory stderr)))
+          (signal 'file-error (list "Wrong stderr" stderr)))
 
         (let* ((buffer
                 (if buffer
                     (get-buffer-create buffer)
                   ;; BUFFER can be nil.  We use a temporary buffer.
                   (generate-new-buffer tramp-temp-buffer-name)))
+               ;; STDERR can also be a file name.
+               (tmpstderr
+                (and stderr
+                     (if (and (stringp stderr) (tramp-tramp-file-p stderr))
+                         (tramp-unquote-file-local-name stderr)
+                       (tramp-make-tramp-temp-file v))))
+               (remote-tmpstderr
+                (and tmpstderr (tramp-make-tramp-file-name v tmpstderr)))
                (program (car command))
                (args (cdr command))
                (command
-                (format "cd %s && exec %s"
+                (format "cd %s && exec %s %s"
                         (tramp-shell-quote-argument localname)
+                        (if tmpstderr (format "2>'%s'" tmpstderr) "")
                         (mapconcat #'tramp-shell-quote-argument
                                    (cons program args) " ")))
                (tramp-process-connection-type
@@ -1029,6 +1077,18 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
                         (ignore-errors
                           (set-process-query-on-exit-flag p (null noquery))
                           (set-marker (process-mark p) (point)))
+                        ;; We must flush them here already; otherwise
+                        ;; `rename-file', `delete-file' or
+                        ;; `insert-file-contents' will fail.
+                        (tramp-flush-connection-property v "process-name")
+                        (tramp-flush-connection-property v "process-buffer")
+                        ;; Copy tmpstderr file.
+                        (when (and (stringp stderr)
+                                   (not (tramp-tramp-file-p stderr)))
+                          (add-function
+                           :after (process-sentinel p)
+                           (lambda (_proc _msg)
+                             (rename-file remote-tmpstderr stderr))))
                         ;; Read initial output.  Remove the first line,
                         ;; which is the command echo.
                         (while
@@ -1037,6 +1097,23 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
                               (not (re-search-forward "[\n]" nil t)))
                           (tramp-accept-process-output p 0))
                         (delete-region (point-min) (point))
+                        ;; Provide error buffer.  This shows only
+                        ;; initial error messages; messages arriving
+                        ;; later on will be inserted when the process
+                        ;; is deleted.  The temporary file will exist
+                        ;; until the process is deleted.
+                        (when (bufferp stderr)
+                          (with-current-buffer stderr
+                            (insert-file-contents-literally
+                             remote-tmpstderr 'visit))
+                          ;; Delete tmpstderr file.
+                          (add-function
+                           :after (process-sentinel p)
+                           (lambda (_proc _msg)
+                             (with-current-buffer stderr
+                               (insert-file-contents-literally
+                                remote-tmpstderr 'visit nil nil 'replace))
+                             (delete-file remote-tmpstderr))))
                         ;; Return process.
                         p))))
 
@@ -1062,7 +1139,7 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
           (read (current-buffer)))
         ":" 'omit)))
    ;; The equivalent to `exec-directory'.
-   `(,(tramp-compat-file-local-name default-directory))))
+   `(,(tramp-file-local-name (expand-file-name default-directory)))))
 
 (defun tramp-adb-get-device (vec)
   "Return full host name from VEC to be used in shell execution.
@@ -1146,11 +1223,14 @@ This happens for Android >= 4.0."
         (while (re-search-forward "\r+$" nil t)
           (replace-match "" nil nil))))))
 
-(defun tramp-adb-send-command-and-check (vec command)
+(defun tramp-adb-send-command-and-check (vec command &optional exit-status)
   "Run COMMAND and check its exit status.
 Sends `echo $?' along with the COMMAND for checking the exit
 status.  If COMMAND is nil, just sends `echo $?'.  Returns nil if
-the exit status is not equal 0, and t otherwise."
+the exit status is not equal 0, and t otherwise.
+
+Optional argument EXIT-STATUS, if non-nil, triggers the return of
+the exit status."
   (tramp-adb-send-command
    vec (if command
            (format "%s; echo tramp_exit_status $?" command)
@@ -1161,7 +1241,9 @@ the exit status is not equal 0, and t otherwise."
        vec 'file-error "Couldn't find exit status of `%s'" command))
     (skip-chars-forward "^ ")
     (prog1
-        (zerop (read (current-buffer)))
+        (if exit-status
+            (read (current-buffer))
+          (zerop (read (current-buffer))))
       (let ((inhibit-read-only t))
         (delete-region (match-beginning 0) (point-max))))))
 
diff --git a/lisp/net/tramp-archive.el b/lisp/net/tramp-archive.el
index b9bf6180a5d..611247ef2cb 100644
--- a/lisp/net/tramp-archive.el
+++ b/lisp/net/tramp-archive.el
@@ -109,7 +109,7 @@
 
 (eval-when-compile (require 'cl-lib))
 ;; Sometimes, compilation fails with "Variable binding depth exceeds
-;; max-specpdl-size".
+;; max-specpdl-size".  Shall be fixed in Emacs 27.
 (eval-and-compile
   (let ((max-specpdl-size (* 2 max-specpdl-size))) (require 'tramp-gvfs)))
 
@@ -318,7 +318,10 @@ arguments to pass to the OPERATION."
 
       (let* ((filename (apply #'tramp-archive-file-name-for-operation
                               operation args))
-             (archive (tramp-archive-file-name-archive filename)))
+             (archive (tramp-archive-file-name-archive filename))
+             ;; Sometimes, it fails with "Variable binding depth exceeds
+             ;; max-specpdl-size".  Shall be fixed in Emacs 27.
+             (max-specpdl-size (* 2 max-specpdl-size)))
 
         ;; `filename' could be a quoted file name.  Or the file
         ;; archive could be a directory, see Bug#30293.
diff --git a/lisp/net/tramp-cache.el b/lisp/net/tramp-cache.el
index 62e25fa1f08..0f2d7a1800f 100644
--- a/lisp/net/tramp-cache.el
+++ b/lisp/net/tramp-cache.el
@@ -514,7 +514,7 @@ for all methods.  Resulting data are derived from connection history."
            tramp-cache-read-persistent-data)
   (condition-case err
       (with-temp-buffer
-        (insert-file-contents tramp-persistency-file-name)
+        (insert-file-contents-literally tramp-persistency-file-name)
         (let ((list (read (current-buffer)))
               (tramp-verbose 0)
               element key item)
diff --git a/lisp/net/tramp-cmds.el b/lisp/net/tramp-cmds.el
index 9d1025b9072..b4dca2321c1 100644
--- a/lisp/net/tramp-cmds.el
+++ b/lisp/net/tramp-cmds.el
@@ -358,7 +358,7 @@ The remote connection identified by SOURCE is flushed by
 
   ;; Append local file name if none is specified.
   (when (string-equal (file-remote-p target) target)
-    (setq target (concat target (file-remote-p source 'localname))))
+    (setq target (concat target (tramp-file-local-name source))))
   ;; Make them directory names.
   (setq source (directory-file-name source)
         target (directory-file-name target))
diff --git a/lisp/net/tramp-compat.el b/lisp/net/tramp-compat.el
index 723b8cfa1e3..3f25afedb99 100644
--- a/lisp/net/tramp-compat.el
+++ b/lisp/net/tramp-compat.el
@@ -41,6 +41,7 @@
 (require 'shell)
 (require 'subr-x)
 
+;; `temporary-file-directory' as function is introduced with Emacs 26.1.
 (declare-function tramp-handle-temporary-file-directory "tramp")
 
 ;; For not existing functions, obsolete functions, or functions with a
diff --git a/lisp/net/tramp-gvfs.el b/lisp/net/tramp-gvfs.el
index 34a234c47f0..ddb535fea6e 100644
--- a/lisp/net/tramp-gvfs.el
+++ b/lisp/net/tramp-gvfs.el
@@ -121,7 +121,10 @@
          (autoload 'zeroconf-init "zeroconf")
          (tramp-compat-funcall 'dbus-get-unique-name :system)
          (tramp-compat-funcall 'dbus-get-unique-name :session)
-         (or (tramp-compat-process-running-p "gvfs-fuse-daemon")
+         (or ;; Until Emacs 25, `process-attributes' could crash Emacs
+             ;; for some processes.  Better we don't check.
+             (<= emacs-major-version 25)
+             (tramp-compat-process-running-p "gvfs-fuse-daemon")
              (tramp-compat-process-running-p "gvfsd-fuse"))))
   "Non-nil when GVFS is available.")
 
@@ -728,6 +731,10 @@ is no information where to trace the message.")
     (tramp-error tramp-gvfs-dbus-event-vector 'file-error "%s" (cadr err))))
 
 (add-hook 'dbus-event-error-functions #'tramp-gvfs-dbus-event-error)
+(add-hook
+ 'tramp-gvfs-unload-hook
+ (lambda ()
+   (remove-hook 'dbus-event-error-functions #'tramp-gvfs-dbus-event-error)))
 
 
 ;; File name primitives.
@@ -1301,10 +1308,11 @@ If FILE-SYSTEM is non-nil, return file system attributes."
            (size (cdr (assoc "filesystem::size" attr)))
            (used (cdr (assoc "filesystem::used" attr)))
            (free (cdr (assoc "filesystem::free" attr))))
-      (when (and (stringp size) (stringp used) (stringp free))
-        (list (string-to-number size)
-              (- (string-to-number size) (string-to-number used))
-              (string-to-number free))))))
+      (when (or size used free)
+        (list (string-to-number (or size "0"))
+              (string-to-number (or free "0"))
+              (- (string-to-number (or size "0"))
+                 (string-to-number (or used "0"))))))))
 
 (defun tramp-gvfs-handle-make-directory (dir &optional parents)
   "Like `make-directory' for Tramp files."
@@ -1341,7 +1349,7 @@ If FILE-SYSTEM is non-nil, return file system attributes."
     (tramp-run-real-handler
      #'rename-file (list filename newname ok-if-already-exists))))
 
-(defun tramp-gvfs-handle-set-file-modes (filename mode)
+(defun tramp-gvfs-handle-set-file-modes (filename mode &optional _flag)
   "Like `set-file-modes' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (tramp-flush-file-properties v localname)
@@ -1350,7 +1358,7 @@ If FILE-SYSTEM is non-nil, return file system attributes."
      (tramp-gvfs-url-file-name (tramp-make-tramp-file-name v))
      "unix::mode" (number-to-string mode))))
 
-(defun tramp-gvfs-handle-set-file-times (filename &optional time)
+(defun tramp-gvfs-handle-set-file-times (filename &optional time _flag)
   "Like `set-file-times' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (tramp-flush-file-properties v localname)
diff --git a/lisp/net/tramp-rclone.el b/lisp/net/tramp-rclone.el
index 9f539850139..fcbd2010a26 100644
--- a/lisp/net/tramp-rclone.el
+++ b/lisp/net/tramp-rclone.el
@@ -478,7 +478,18 @@ file names."
            (with-tramp-connection-property
                (tramp-get-connection-process vec) "rclone-pid"
              (catch 'pid
-               (dolist (pid (list-system-processes)) ;; "pidof rclone" ?
+               (dolist
+                   (pid
+                    ;; Until Emacs 25, `process-attributes' could
+                    ;; crash Emacs for some processes.  So we use
+                    ;; "pidof", which might not work everywhere.
+                    (if (<= emacs-major-version 25)
+                        (let ((default-directory temporary-file-directory))
+                          (mapcar
+                           #'string-to-number
+                           (split-string
+                            (shell-command-to-string "pidof rclone"))))
+                      (list-system-processes)))
                  (and (string-match-p
                        (regexp-quote
                         (format "rclone mount %s:" (tramp-file-name-host vec)))
@@ -564,7 +575,7 @@ connection if a previous connection has died for some reason."
                  ,(tramp-rclone-mount-point vec)
                  ;; This could be nil.
                  ,(tramp-get-method-parameter vec 'tramp-mount-args))))
-        (while (not (file-exists-p (tramp-make-tramp-file-name vec 'localname)))
+        (while (not (file-exists-p (tramp-make-tramp-file-name vec 'noloc)))
           (tramp-cleanup-connection vec 'keep-debug 'keep-password))
 
         ;; Mark it as connected.
diff --git a/lisp/net/tramp-sh.el b/lisp/net/tramp-sh.el
index af97328b3d3..9e8a3168fd7 100644
--- a/lisp/net/tramp-sh.el
+++ b/lisp/net/tramp-sh.el
@@ -36,6 +36,7 @@
 
 (declare-function dired-remove-file "dired-aux")
 (defvar dired-compress-file-suffixes)
+(defvar process-file-return-signal-string)
 (defvar vc-handled-backends)
 (defvar vc-bzr-program)
 (defvar vc-git-program)
@@ -537,12 +538,13 @@ based on the Tramp and Emacs versions, and should not be set here."
 
 ;;;###tramp-autoload
 (defcustom tramp-sh-extra-args
-  '(("/bash\\'" . "-norc -noprofile")
+  '(("/bash\\'" . "-noediting -norc -noprofile")
     ("/zsh\\'" . "-f +Z -V"))
   "Alist specifying extra arguments to pass to the remote shell.
 Entries are (REGEXP . ARGS) where REGEXP is a regular expression
 matching the shell file name and ARGS is a string specifying the
-arguments.
+arguments.  These arguments shall disable line editing, see
+`tramp-open-shell'.
 
 This variable is only used when Tramp needs to start up another shell
 for tilde expansion.  The extra arguments should typically prevent the
@@ -866,8 +868,12 @@ Escape sequence %s is replaced with name of Perl binary.")
   "Perl program to use for decoding a file.
 Escape sequence %s is replaced with name of Perl binary.")
 
+(defconst tramp-hexdump-encode "%h -v -e '16/1 \" %%02x\" \"\\n\"'"
+  "`hexdump' program to use for encoding a file.
+This string is passed to `format', so percent characters need to be doubled.")
+
 (defconst tramp-awk-encode
-  "od -v -t x1 -A n | busybox awk '\\
+  "%a '\\
 BEGIN {
   b64 = \"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/\"
   b16 = \"0123456789abcdef\"
@@ -897,11 +903,25 @@ END {
   }
   printf tail
 }'"
-  "Awk program to use for encoding a file.
+  "`awk' program to use for encoding a file.
+This string is passed to `format', so percent characters need to be doubled.")
+
+(defconst tramp-hexdump-awk-encode
+  (format "%s | %s" tramp-hexdump-encode tramp-awk-encode)
+  "`hexdump' / `awk' pipe to use for encoding a file.
+This string is passed to `format', so percent characters need to be doubled.")
+
+(defconst tramp-od-encode "%o -v -t x1 -A n"
+  "`od' program to use for encoding a file.
+This string is passed to `format', so percent characters need to be doubled.")
+
+(defconst tramp-od-awk-encode
+  (format "%s | %s" tramp-od-encode tramp-awk-encode)
+  "`od' / `awk' pipe to use for encoding a file.
 This string is passed to `format', so percent characters need to be doubled.")
 
 (defconst tramp-awk-decode
-  "busybox awk '\\
+  "%a '\\
 BEGIN {
   b64 = \"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/\"
 }
@@ -926,12 +946,6 @@ BEGIN {
   "Awk program to use for decoding a file.
 This string is passed to `format', so percent characters need to be doubled.")
 
-(defconst tramp-awk-coding-test
-  "test -c /dev/zero && \
-od -v -t x1 -A n </dev/null && \
-busybox awk '{}' </dev/null"
-  "Test command for checking `tramp-awk-encode' and `tramp-awk-decode'.")
-
 (defconst tramp-vc-registered-read-file-names
   "echo \"(\"
 while read file; do
@@ -1051,9 +1065,7 @@ component is used as the target of the symlink."
       (let ((non-essential t))
         (when (and (tramp-tramp-file-p target)
                    (tramp-file-name-equal-p v (tramp-dissect-file-name target)))
-          (setq target
-                (tramp-file-name-localname
-                 (tramp-dissect-file-name (expand-file-name target))))))
+          (setq target (tramp-file-local-name (expand-file-name target)))))
 
       ;; If TARGET is still remote, quote it.
       (if (tramp-tramp-file-p target)
@@ -1263,8 +1275,8 @@ component is used as the target of the symlink."
 (defun tramp-do-file-attributes-with-ls (vec localname &optional id-format)
   "Implement `file-attributes' for Tramp files using the ls(1) command."
   (let (symlinkp dirp
-                 res-inode res-filemodes res-numlinks
-                 res-uid res-gid res-size res-symlink-target)
+        res-inode res-filemodes res-numlinks
+        res-uid res-gid res-size res-symlink-target)
     (tramp-message vec 5 "file attributes with ls: %s" localname)
     ;; We cannot send all three commands combined, it could exceed
     ;; NAME_MAX or PATH_MAX.  Happened on macOS, for example.
@@ -1368,18 +1380,11 @@ component is used as the target of the symlink."
    (format
     (eval-when-compile
       (concat
-       ;; On Opsware, pdksh (which is the true name of ksh there)
-       ;; doesn't parse correctly the sequence "((".  Therefore, we
-       ;; add a space.  Apostrophes in the stat output are masked as
+       ;; Apostrophes in the stat output are masked as
        ;; `tramp-stat-marker', in order to make a proper shell escape
        ;; of them in file names.
-       "( (%s %s || %s -h %s) && (%s -c "
-       "'((%s%%N%s) %%h %s %s %%X %%Y %%Z %%s %s%%A%s t %%i -1)' "
-       "%s | sed -e 's/\"/\\\\\"/g' -e 's/%s/\"/g') || echo nil)"))
-    (tramp-get-file-exists-command vec)
-    (tramp-shell-quote-argument localname)
-    (tramp-get-test-command vec)
-    (tramp-shell-quote-argument localname)
+       "(%s -c '((%s%%N%s) %%h %s %s %%X %%Y %%Z %%s %s%%A%s t %%i -1)' %s |"
+       " sed -e 's/\"/\\\\\"/g' -e 's/%s/\"/g')"))
     (tramp-get-remote-stat vec)
     tramp-stat-marker tramp-stat-marker
     (if (eq id-format 'integer)
@@ -1390,7 +1395,8 @@ component is used as the target of the symlink."
       (eval-when-compile (concat tramp-stat-marker "%G" tramp-stat-marker)))
     tramp-stat-marker tramp-stat-marker
     (tramp-shell-quote-argument localname)
-    tramp-stat-quoted-marker)))
+    tramp-stat-quoted-marker)
+   'noerror))
 
 (defun tramp-sh-handle-set-visited-file-modtime (&optional time-list)
   "Like `set-visited-file-modtime' for Tramp files."
@@ -1468,7 +1474,7 @@ of."
              ;; only if that agrees with the buffer's record.
              (t (tramp-compat-time-equal-p mt tramp-time-doesnt-exist)))))))))
 
-(defun tramp-sh-handle-set-file-modes (filename mode)
+(defun tramp-sh-handle-set-file-modes (filename mode &optional _flag)
   "Like `set-file-modes' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (tramp-flush-file-properties v localname)
@@ -1478,7 +1484,7 @@ of."
      (format "chmod %o %s" mode (tramp-shell-quote-argument localname))
      "Error while changing file's mode %s" filename)))
 
-(defun tramp-sh-handle-set-file-times (filename &optional time)
+(defun tramp-sh-handle-set-file-times (filename &optional time _flag)
   "Like `set-file-times' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (when (tramp-get-remote-touch v)
@@ -2171,8 +2177,8 @@ the uid and gid from FILENAME."
                             v 'file-error
                             "Unknown operation `%s', must be `copy' or `rename'"
                             op))))
-             (localname1 (tramp-compat-file-local-name filename))
-             (localname2 (tramp-compat-file-local-name newname))
+             (localname1 (tramp-file-local-name filename))
+             (localname2 (tramp-file-local-name newname))
              (prefix (file-remote-p (if t1 filename newname)))
              cmd-result)
         (when (and (eq op 'copy) (file-directory-p filename))
@@ -2796,8 +2802,11 @@ the result will be a local, non-Tramp, file name."
 ;; We use BUFFER also as connection buffer during setup. Because of
 ;; this, its original contents must be saved, and restored once
 ;; connection has been setup.
+;; The complete STDERR buffer is available only when the process has
+;; terminated.
 (defun tramp-sh-handle-make-process (&rest args)
-  "Like `make-process' for Tramp files."
+  "Like `make-process' for Tramp files.
+STDERR can also be a file name."
   (when args
     (with-parsed-tramp-file-name (expand-file-name default-directory) nil
       (let ((name (plist-get args :name))
@@ -2829,14 +2838,23 @@ the result will be a local, non-Tramp, file name."
           (signal 'wrong-type-argument (list #'functionp sentinel)))
         (unless (or (null stderr) (bufferp stderr) (stringp stderr))
           (signal 'wrong-type-argument (list #'stringp stderr)))
+        (when (and (stringp stderr) (tramp-tramp-file-p stderr)
+                   (not (tramp-equal-remote default-directory stderr)))
+          (signal 'file-error (list "Wrong stderr" stderr)))
 
         (let* ((buffer
                 (if buffer
                     (get-buffer-create buffer)
                   ;; BUFFER can be nil.  We use a temporary buffer.
                   (generate-new-buffer tramp-temp-buffer-name)))
-               (stderr (and stderr (get-buffer-create stderr)))
-               (tmpstderr (and stderr (tramp-make-tramp-temp-file v)))
+               ;; STDERR can also be a file name.
+               (tmpstderr
+                (and stderr
+                     (if (and (stringp stderr) (tramp-tramp-file-p stderr))
+                         (tramp-unquote-file-local-name stderr)
+                       (tramp-make-tramp-temp-file v))))
+               (remote-tmpstderr
+                (and tmpstderr (tramp-make-tramp-file-name v tmpstderr)))
                (program (car command))
                (args (cdr command))
                ;; When PROGRAM matches "*sh", and the first arg is
@@ -2965,21 +2983,35 @@ the result will be a local, non-Tramp, file name."
                       (ignore-errors
                         (set-process-query-on-exit-flag p (null noquery))
                         (set-marker (process-mark p) (point)))
+                      ;; We must flush them here already; otherwise
+                      ;; `rename-file', `delete-file' or
+                      ;; `insert-file-contents' will fail.
+                      (tramp-flush-connection-property v "process-name")
+                      (tramp-flush-connection-property v "process-buffer")
+                      ;; Copy tmpstderr file.
+                      (when (and (stringp stderr)
+                                 (not (tramp-tramp-file-p stderr)))
+                        (add-function
+                         :after (process-sentinel p)
+                         (lambda (_proc _msg)
+                           (rename-file remote-tmpstderr stderr))))
                       ;; Provide error buffer.  This shows only
                       ;; initial error messages; messages arriving
-                      ;; later on shall be inserted by `auto-revert'.
-                      ;; The temporary file will still be existing.
-                      ;; TODO: Write a sentinel, which deletes the
-                      ;; temporary file.
-                      (when tmpstderr
-                        ;; We must flush them here already; otherwise
-                        ;; `insert-file-contents' will fail.
-                        (tramp-flush-connection-property v "process-name")
-                        (tramp-flush-connection-property v "process-buffer")
+                      ;; later on will be inserted when the process is
+                      ;; deleted.  The temporary file will exist until
+                      ;; the process is deleted.
+                      (when (bufferp stderr)
                         (with-current-buffer stderr
-                          (insert-file-contents
-                           (tramp-make-tramp-file-name v tmpstderr) 'visit)
-                          (auto-revert-mode)))
+                          (insert-file-contents-literally remote-tmpstderr))
+                        ;; Delete tmpstderr file.
+                        (add-function
+                         :after (process-sentinel p)
+                         (lambda (_proc _msg)
+                           (when (file-exists-p remote-tmpstderr)
+                             (with-current-buffer stderr
+                               (insert-file-contents-literally
+                                remote-tmpstderr nil nil nil 'replace))
+                             (delete-file remote-tmpstderr)))))
                       ;; Return process.
                       p)))
 
@@ -2992,6 +3024,65 @@ the result will be a local, non-Tramp, file name."
               (tramp-flush-connection-property v "process-name")
               (tramp-flush-connection-property v "process-buffer"))))))))
 
+(defun tramp-sh-get-signal-strings (vec)
+  "Strings to return by `process-file' in case of signals."
+  (with-tramp-connection-property
+      vec
+      (concat
+       "signal-strings-" (tramp-get-method-parameter vec 'tramp-remote-shell))
+    (let ((default-directory (tramp-make-tramp-file-name vec 'localname))
+          process-file-return-signal-string signals res result)
+      (setq signals
+            (append
+             '(0) (split-string (shell-command-to-string "kill -l") nil 'omit)))
+      ;; Sanity check.  Sometimes, the first entry is "0", although we
+      ;; don't expect it.  Remove it.
+      (when (and (stringp (cadr signals)) (string-equal "0" (cadr signals)))
+        (setcdr signals (cddr signals)))
+      ;; Sanity check.  "kill -l" shall have returned just the signal
+      ;; names.  Some shells don't, like the one in "docker alpine".
+      (let (signal-hook-function)
+        (condition-case nil
+            (dolist (sig (cdr signals))
+              (unless (string-match-p "^[[:alnum:]+-]+$" sig)
+                (error nil)))
+          (error (setq signals '(0)))))
+      (dotimes (i 128)
+        (push
+         (cond
+          ;; Some predefined values, which aren't reported sometimes,
+          ;; or would raise problems (all Stopped signals).
+          ((= i 0) 0)
+          ((string-equal (nth i signals) "HUP") "Hangup")
+          ((string-equal (nth i signals) "INT") "Interrupt")
+          ((string-equal (nth i signals) "QUIT") "Quit")
+          ((string-equal (nth i signals) "STOP") "Stopped (signal)")
+          ((string-equal (nth i signals) "TSTP") "Stopped")
+          ((string-equal (nth i signals) "TTIN") "Stopped (tty input)")
+          ((string-equal (nth i signals) "TTOU") "Stopped (tty output)")
+          (t (setq res
+                   (if (null (nth i signals))
+                       ""
+                     (tramp-send-command
+                      vec
+                      (format
+                       "%s %s %s"
+                       (tramp-get-method-parameter vec 'tramp-remote-shell)
+                       (mapconcat
+                        #'identity
+                        (tramp-get-method-parameter vec 'tramp-remote-shell-args)
+                        " ")
+                       (tramp-shell-quote-argument (format "kill -%d $$" i))))
+                     (with-current-buffer (tramp-get-connection-buffer vec)
+                       (goto-char (point-min))
+                       (buffer-substring (point-at-bol) (point-at-eol)))))
+             (if (string-equal res "")
+                 (format "Signal %d" i)
+               res)))
+         result))
+      ;; Due to Bug#41287, we cannot add this to the `dotimes' clause.
+      (reverse result))))
+
 (defun tramp-sh-handle-process-file
   (program &optional infile destination display &rest args)
   "Like `process-file' for Tramp files."
@@ -3028,7 +3119,7 @@ the result will be a local, non-Tramp, file name."
         (setq infile (expand-file-name infile))
         (if (tramp-equal-remote default-directory infile)
             ;; INFILE is on the same remote host.
-            (setq input (with-parsed-tramp-file-name infile nil localname))
+            (setq input (tramp-file-local-name infile))
           ;; INFILE must be copied to remote host.
           (setq input (tramp-make-tramp-temp-file v)
                 tmpinput (tramp-make-tramp-file-name v input 'nohop))
@@ -3059,8 +3150,7 @@ the result will be a local, non-Tramp, file name."
           (setcar (cdr destination) (expand-file-name (cadr destination)))
           (if (tramp-equal-remote default-directory (cadr destination))
               ;; stderr is on the same remote host.
-              (setq stderr (with-parsed-tramp-file-name
-                               (cadr destination) nil localname))
+              (setq stderr (tramp-file-local-name (cadr destination)))
             ;; stderr must be copied to remote host.  The temporary
             ;; file must be deleted after execution.
             (setq stderr (tramp-make-tramp-temp-file v)
@@ -3078,13 +3168,12 @@ the result will be a local, non-Tramp, file name."
       ;; directory.
       (condition-case nil
           (unwind-protect
-              (setq ret
-                    (if (tramp-send-command-and-check
-                         v (format "cd %s && %s"
-                                   (tramp-shell-quote-argument localname)
-                                   command)
-                         t t)
-                        0 1))
+              (setq ret (tramp-send-command-and-check
+                         v (format
+                            "cd %s && %s"
+                            (tramp-shell-quote-argument localname) command)
+                         t t t))
+            (unless (natnump ret) (setq ret 1))
             ;; We should add the output anyway.
             (when outbuf
               (with-current-buffer outbuf
@@ -3102,6 +3191,12 @@ the result will be a local, non-Tramp, file name."
          (kill-buffer (tramp-get-connection-buffer v))
          (setq ret 1)))
 
+      ;; Handle signals.  `process-file-return-signal-string' exists
+      ;; since Emacs 28.1.
+      (when (and (bound-and-true-p process-file-return-signal-string)
+                 (natnump ret) (>= ret 128))
+        (setq ret (nth (- ret 128) (tramp-sh-get-signal-strings v))))
+
       ;; Provide error file.
       (when tmpstderr (rename-file tmpstderr (cadr destination) t))
 
@@ -3122,7 +3217,7 @@ the result will be a local, non-Tramp, file name."
   (append
    (tramp-get-remote-path (tramp-dissect-file-name default-directory))
    ;; The equivalent to `exec-directory'.
-   `(,(tramp-compat-file-local-name default-directory))))
+   `(,(tramp-file-local-name (expand-file-name default-directory)))))
 
 (defun tramp-sh-handle-file-local-copy (filename)
   "Like `file-local-copy' for Tramp files."
@@ -3258,7 +3353,8 @@ the result will be a local, non-Tramp, file name."
 
           ;; If `append' is non-nil, we copy the file locally, and let
           ;; the native `write-region' implementation do the job.
-          (when append (copy-file filename tmpfile 'ok))
+          (when (and append (file-exists-p filename))
+            (copy-file filename tmpfile 'ok))
 
           ;; We say `no-message' here because we don't want the
           ;; visited file modtime data to be clobbered from the temp
@@ -3981,23 +4077,30 @@ whether it exists and if so, it is added to the environment
 variable PATH."
   (let ((command
          (format
-          "PATH=%s; export PATH" (string-join (tramp-get-remote-path vec) ":")))
+          "PATH=%s && export PATH" (string-join (tramp-get-remote-path vec) ":")))
         (pipe-buf
-         (or (with-tramp-connection-property vec "pipe-buf"
-               (tramp-send-command-and-read
-                vec "getconf PIPE_BUF / 2>/dev/null || echo nil" 'noerror))
-             4096))
-        tmpfile)
+         (with-tramp-connection-property vec "pipe-buf"
+           (tramp-send-command-and-read
+            vec "getconf PIPE_BUF / 2>/dev/null || echo 4096" 'noerror)))
+        tmpfile chunk chunksize)
     (tramp-message vec 5 "Setting $PATH environment variable")
     (if (< (length command) pipe-buf)
         (tramp-send-command vec command)
-      ;; Use a temporary file.
-      (setq tmpfile
-            (tramp-make-tramp-file-name vec (tramp-make-tramp-temp-file vec)))
-      (write-region command nil tmpfile)
-      (tramp-send-command
-       vec (format ". %s" (tramp-compat-file-local-name tmpfile)))
-      (delete-file tmpfile))))
+      ;; Use a temporary file.  We cannot use `write-region' because
+      ;; setting the remote path happens in the early connection
+      ;; handshake, and not all external tools are determined yet.
+      (setq command (concat command "\n")
+            tmpfile (tramp-make-tramp-temp-file vec))
+      (while (not (string-empty-p command))
+        (setq chunksize (min (length command) (/ pipe-buf 2))
+              chunk (substring command 0 chunksize)
+              command (substring command chunksize))
+        (tramp-send-command vec (format
+                                 "echo -n %s >>%s"
+                                 (tramp-shell-quote-argument chunk)
+                                 (tramp-shell-quote-argument tmpfile))))
+      (tramp-send-command vec (format ". %s" tmpfile))
+      (tramp-send-command vec (format "rm -f %s" tmpfile)))))
 
 ;; ------------------------------------------------------------
 ;; -- Communication with external shell --
@@ -4069,54 +4172,54 @@ file exists and nonzero exit status otherwise."
 
 (defun tramp-open-shell (vec shell)
   "Open shell SHELL."
+  ;; Find arguments for this shell.
   (with-tramp-progress-reporter
       vec 5 (format-message "Opening remote shell `%s'" shell)
-    ;; Find arguments for this shell.
-    (let ((extra-args (tramp-get-sh-extra-args shell)))
-      ;; doesn't know about and thus /bin/sh will display a strange
-      ;; prompt.  For example, if $PS1 has "${CWD}" in the value, then
-      ;; ksh will display the current working directory but /bin/sh
-      ;; will display a dollar sign.  The following command line sets
-      ;; $PS1 to a sane value, and works under Bourne-ish shells as
-      ;; well as csh-like shells.  We also unset the variable $ENV
-      ;; because that is read by some sh implementations (eg, bash
-      ;; when called as sh) on startup; this way, we avoid the startup
-      ;; file clobbering $PS1.  $PROMPT_COMMAND is another way to set
-      ;; the prompt in /bin/bash, it must be discarded as well.
-      ;; $HISTFILE is set according to `tramp-histfile-override'.
-      ;; $TERM and $INSIDE_EMACS set here to ensure they have the
-      ;; correct values when the shell starts, not just processes
-      ;; run within the shell.  (Which processes include our
-      ;; initial probes to ensure the remote shell is usable.)
-      (tramp-send-command
-       vec (format
-            (eval-when-compile
-              (concat
-               "exec env TERM='%s' INSIDE_EMACS='%s,tramp:%s' "
-               "ENV=%s %s PROMPT_COMMAND='' PS1=%s PS2='' PS3='' %s %s"))
-            tramp-terminal-type
-            emacs-version tramp-version  ; INSIDE_EMACS
-            (or (getenv-internal "ENV" tramp-remote-process-environment) "")
-            (if (stringp tramp-histfile-override)
-                (format "HISTFILE=%s"
-                        (tramp-shell-quote-argument tramp-histfile-override))
-              (if tramp-histfile-override
-                  "HISTFILE='' HISTFILESIZE=0 HISTSIZE=0"
-                ""))
-            (tramp-shell-quote-argument tramp-end-of-output)
-            shell (or extra-args ""))
-       t)
-      ;; Check proper HISTFILE setting.  We give up when not working.
-      (when (and (stringp tramp-histfile-override)
-                 (file-name-directory tramp-histfile-override))
-        (tramp-barf-unless-okay
-         vec
-         (format
-          "(cd %s)"
-          (tramp-shell-quote-argument
-           (file-name-directory tramp-histfile-override)))
-         "`tramp-histfile-override' uses invalid file `%s'"
-         tramp-histfile-override)))
+    ;; It is useful to set the prompt in the following command because
+    ;; some people have a setting for $PS1 which /bin/sh doesn't know
+    ;; about and thus /bin/sh will display a strange prompt.  For
+    ;; example, if $PS1 has "${CWD}" in the value, then ksh will
+    ;; display the current working directory but /bin/sh will display
+    ;; a dollar sign.  The following command line sets $PS1 to a sane
+    ;; value, and works under Bourne-ish shells as well as csh-like
+    ;; shells.  We also unset the variable $ENV because that is read
+    ;; by some sh implementations (eg, bash when called as sh) on
+    ;; startup; this way, we avoid the startup file clobbering $PS1.
+    ;; $PROMPT_COMMAND is another way to set the prompt in /bin/bash,
+    ;; it must be discarded as well.  $HISTFILE is set according to
+    ;; `tramp-histfile-override'.  $TERM and $INSIDE_EMACS set here to
+    ;; ensure they have the correct values when the shell starts, not
+    ;; just processes run within the shell.  (Which processes include
+    ;; our initial probes to ensure the remote shell is usable.)
+    (tramp-send-command
+     vec (format
+          (eval-when-compile
+            (concat
+             "exec env TERM='%s' INSIDE_EMACS='%s,tramp:%s' "
+             "ENV=%s %s PROMPT_COMMAND='' PS1=%s PS2='' PS3='' %s %s"))
+          tramp-terminal-type
+          emacs-version tramp-version  ; INSIDE_EMACS
+          (or (getenv-internal "ENV" tramp-remote-process-environment) "")
+          (if (stringp tramp-histfile-override)
+              (format "HISTFILE=%s"
+                      (tramp-shell-quote-argument tramp-histfile-override))
+            (if tramp-histfile-override
+                "HISTFILE='' HISTFILESIZE=0 HISTSIZE=0"
+              ""))
+          (tramp-shell-quote-argument tramp-end-of-output)
+          shell (or (tramp-get-sh-extra-args shell) ""))
+     t)
+    ;; Check proper HISTFILE setting.  We give up when not working.
+    (when (and (stringp tramp-histfile-override)
+               (file-name-directory tramp-histfile-override))
+      (tramp-barf-unless-okay
+       vec
+       (format
+        "(cd %s)"
+        (tramp-shell-quote-argument
+         (file-name-directory tramp-histfile-override)))
+       "`tramp-histfile-override' uses invalid file `%s'"
+       tramp-histfile-override))
 
     (tramp-set-connection-property
      (tramp-get-connection-process vec) "remote-shell" shell)))
@@ -4187,9 +4290,16 @@ process to set up.  VEC specifies the connection."
   (let ((tramp-end-of-output tramp-initial-end-of-output)
         (case-fold-search t))
     (tramp-open-shell vec (tramp-get-method-parameter vec 'tramp-remote-shell))
+    (tramp-message vec 5 "Setting up remote shell environment")
+
+    ;; Disable line editing.
+    (tramp-send-command vec "set +o vi +o emacs" t)
+
+    ;; Dump option settings in the traces.
+    (when (>= tramp-verbose 9)
+      (tramp-send-command vec "set -o" t))
 
     ;; Disable echo expansion.
-    (tramp-message vec 5 "Setting up remote shell environment")
     (tramp-send-command
      vec "stty -inlcr -onlcr -echo kill '^U' erase '^H'" t)
     ;; Check whether the echo has really been disabled.  Some
@@ -4259,8 +4369,6 @@ process to set up.  VEC specifies the connection."
         (tramp-message
          vec 5 "Setting coding system to `%s' and `%s'" cs-decode cs-encode)))
 
-    (tramp-send-command vec "set +o vi +o emacs" t)
-
     ;; Check whether the remote host suffers from buggy
     ;; `send-process-string'.  This is known for FreeBSD (see comment
     ;; in `send_process', file process.c).  I've tested sending 624
@@ -4383,7 +4491,7 @@ and end of region, and are expected to replace the region contents
 with the encoded or decoded results, respectively.")
 
 (defconst tramp-remote-coding-commands
-  `((b64 "base64" "base64 -d -i")
+  '((b64 "base64" "base64 -d -i")
     ;; "-i" is more robust with older base64 from GNU coreutils.
     ;; However, I don't know whether all base64 versions do supports
     ;; this option.
@@ -4394,8 +4502,9 @@ with the encoded or decoded results, respectively.")
     (b64 "recode data..base64" "recode base64..data")
     (b64 tramp-perl-encode-with-module tramp-perl-decode-with-module)
     (b64 tramp-perl-encode tramp-perl-decode)
-    ;; This is painful slow, so we put it on the end.
-    (b64 tramp-awk-encode tramp-awk-decode ,tramp-awk-coding-test)
+    ;; These are painfully slow, so we put them on the end.
+    (b64 tramp-hexdump-awk-encode tramp-awk-decode)
+    (b64 tramp-od-awk-encode tramp-awk-decode)
     (uu  "uuencode xxx" "uudecode -o /dev/stdout" "test -c /dev/stdout")
     (uu  "uuencode xxx" "uudecode -o -")
     (uu  "uuencode xxx" "uudecode -p")
@@ -4421,6 +4530,8 @@ Perl or Shell implementation for this functionality.  This
 program will be transferred to the remote host, and it is
 available as shell function with the same name.  A \"%t\" format
 specifier in the variable value denotes a temporary file.
+\"%a\", \"%h\" and \"%o\" format specifiers are replaced by the
+respective `awk', `hexdump' and `od' commands.
 
 The optional TEST command can be used for further tests, whether
 ENCODING and DECODING are applicable.")
@@ -4471,11 +4582,6 @@ Goes through the list `tramp-local-coding-commands' and
                      vec 5 "Checking remote test command `%s'" rem-test)
                     (unless (tramp-send-command-and-check vec rem-test t)
                       (throw 'wont-work-remote nil)))
-                  ;; Check if remote perl exists when necessary.
-                  (when (and (symbolp rem-enc)
-                             (string-match-p "perl" (symbol-name rem-enc))
-                             (not (tramp-get-remote-perl vec)))
-                    (throw 'wont-work-remote nil))
                   ;; Check if remote encoding and decoding commands can be
                   ;; called remotely with null input and output.  This makes
                   ;; sure there are no syntax errors and the command is really
@@ -4485,10 +4591,36 @@ Goes through the list `tramp-local-coding-commands' and
                   ;; redirecting "mimencode" output to /dev/null, then as root
                   ;; it might change the permissions of /dev/null!
                   (unless (stringp rem-enc)
-                    (let ((name (symbol-name rem-enc)))
+                    (let ((name (symbol-name rem-enc))
+                          (value (symbol-value rem-enc)))
+                      ;; Check if remote perl exists when necessary.
+                      (and (string-match-p "perl" name)
+                           (not (tramp-get-remote-perl vec))
+                           (throw 'wont-work-remote nil))
+                      ;; Check if remote awk exists when necessary.
+                      (and (string-match-p "\\(^\\|[^%]\\)%a" value)
+                           (not (tramp-get-remote-awk vec))
+                           (throw 'wont-work-remote nil))
+                      ;; Check if remote hexdump exists when necessary.
+                      (and (string-match-p "\\(^\\|[^%]\\)%h" value)
+                           (not (tramp-get-remote-hexdump vec))
+                           (throw 'wont-work-remote nil))
+                      ;; Check if remote od exists when necessary.
+                      (and (string-match-p "\\(^\\|[^%]\\)%o" value)
+                           (not (tramp-get-remote-od vec))
+                           (throw 'wont-work-remote nil))
                       (while (string-match "-" name)
                         (setq name (replace-match "_" nil t name)))
-                      (tramp-maybe-send-script vec (symbol-value rem-enc) name)
+                      (when (string-match-p "\\(^\\|[^%]\\)%[aho]" value)
+                        (setq value
+                              (format-spec
+                               value
+                               (format-spec-make
+                                ?a (tramp-get-remote-awk vec)
+                                ?h (tramp-get-remote-hexdump vec)
+                                ?o (tramp-get-remote-od vec)))
+                              value (replace-regexp-in-string "%" "%%" value)))
+                      (tramp-maybe-send-script vec value name)
                       (setq rem-enc name)))
                   (tramp-message
                    vec 5
@@ -4503,6 +4635,15 @@ Goes through the list `tramp-local-coding-commands' and
                           tmpfile)
                       (while (string-match "-" name)
                         (setq name (replace-match "_" nil t name)))
+                      (when (string-match-p "\\(^\\|[^%]\\)%[aho]" value)
+                        (setq value
+                              (format-spec
+                               value
+                               (format-spec-make
+                                ?a (tramp-get-remote-awk vec)
+                                ?h (tramp-get-remote-hexdump vec)
+                                ?o (tramp-get-remote-od vec)))
+                              value (replace-regexp-in-string "%" "%%" value)))
                       (when (string-match-p "\\(^\\|[^%]\\)%t" value)
                         (setq tmpfile
                               (make-temp-name
@@ -4513,7 +4654,7 @@ Goes through the list `tramp-local-coding-commands' and
                               (format-spec
                                value
                                (format-spec-make
-                                ?t (tramp-compat-file-local-name tmpfile)))))
+                                ?t (tramp-file-local-name tmpfile)))))
                       (tramp-maybe-send-script vec value name)
                       (setq rem-dec name)))
                   (tramp-message
@@ -4796,7 +4937,7 @@ If there is just some editing, retry it after 5 seconds."
          vec 5 "Cannot timeout session, trying it again in %s seconds." 5)
         (run-at-time 5 nil 'tramp-timeout-session vec))
     (tramp-message
-     vec 3 "Timeout session %s" (tramp-make-tramp-file-name vec 'localname))
+     vec 3 "Timeout session %s" (tramp-make-tramp-file-name vec 'noloc))
     (tramp-cleanup-connection vec 'keep-debug)))
 
 (defun tramp-maybe-open-connection (vec)
@@ -5116,7 +5257,7 @@ function waits for output unless NOOUTPUT is set."
       found)))
 
 (defun tramp-send-command-and-check
-  (vec command &optional subshell dont-suppress-err)
+  (vec command &optional subshell dont-suppress-err exit-status)
   "Run COMMAND and check its exit status.
 Send `echo $?' along with the COMMAND for checking the exit status.
 If COMMAND is nil, just send `echo $?'.  Return t if the exit
@@ -5124,7 +5265,9 @@ status is 0, and nil otherwise.
 
 If the optional argument SUBSHELL is non-nil, the command is
 executed in a subshell, ie surrounded by parentheses.  If
-DONT-SUPPRESS-ERR is non-nil, stderr won't be sent to /dev/null."
+DONT-SUPPRESS-ERR is non-nil, stderr won't be sent to /dev/null.
+Optional argument EXIT-STATUS, if non-nil, triggers the return of
+the exit status."
   (tramp-send-command
    vec
    (concat (if subshell "( " "")
@@ -5138,7 +5281,9 @@ DONT-SUPPRESS-ERR is non-nil, stderr won't be sent to /dev/null."
        vec 'file-error "Couldn't find exit status of `%s'" command))
     (skip-chars-forward "^ ")
     (prog1
-        (zerop (read (current-buffer)))
+        (if exit-status
+            (read (current-buffer))
+          (zerop (read (current-buffer))))
       (let ((inhibit-read-only t))
         (delete-region (match-beginning 0) (point-max))))))
 
@@ -5171,7 +5316,10 @@ raises an error."
                     command marker (buffer-string))))))
       ;; Read the expression.
       (condition-case nil
-          (prog1 (read (current-buffer))
+          (prog1
+              (let ((signal-hook-function
+                     (unless noerror signal-hook-function)))
+                (read (current-buffer)))
             ;; Error handling.
             (when (re-search-forward "\\S-" (point-at-eol) t)
               (error nil)))
@@ -5594,7 +5742,7 @@ This command is returned only if `delete-by-moving-to-trash' is non-nil."
            "%s -t %s %s"
            result
            (format-time-string "%Y%m%d%H%M.%S")
-           (tramp-compat-file-local-name tmpfile))))
+           (tramp-file-local-name tmpfile))))
         (delete-file tmpfile))
       result)))
 
@@ -5769,6 +5917,47 @@ ID-FORMAT valid values are `string' and `integer'."
         tramp-unknown-id-string)
        (t res)))))
 
+(defun tramp-get-remote-busybox (vec)
+  "Determine remote `busybox' command."
+  (with-tramp-connection-property vec "busybox"
+    (tramp-message vec 5 "Finding a suitable `busybox' command")
+    (tramp-find-executable vec "busybox" (tramp-get-remote-path vec))))
+
+(defun tramp-get-remote-awk (vec)
+  "Determine remote `awk' command."
+  (with-tramp-connection-property vec "awk"
+    (tramp-message vec 5 "Finding a suitable `awk' command")
+    (or (tramp-find-executable vec "awk" (tramp-get-remote-path vec))
+        (let* ((busybox (tramp-get-remote-busybox vec))
+               (command (format "%s %s" busybox "awk")))
+          (and busybox
+               (tramp-send-command-and-check
+                vec (concat command " {} </dev/null"))
+               command)))))
+
+(defun tramp-get-remote-hexdump (vec)
+  "Determine remote `hexdump' command."
+  (with-tramp-connection-property vec "hexdump"
+    (tramp-message vec 5 "Finding a suitable `hexdump' command")
+    (or (tramp-find-executable vec "hexdump" (tramp-get-remote-path vec))
+        (let* ((busybox (tramp-get-remote-busybox vec))
+               (command (format "%s %s" busybox "hexdump")))
+          (and busybox
+               (tramp-send-command-and-check vec (concat command " </dev/null"))
+               command)))))
+
+(defun tramp-get-remote-od (vec)
+  "Determine remote `od' command."
+  (with-tramp-connection-property vec "od"
+    (tramp-message vec 5 "Finding a suitable `od' command")
+    (or (tramp-find-executable vec "od" (tramp-get-remote-path vec))
+        (let* ((busybox (tramp-get-remote-busybox vec))
+               (command (format "%s %s" busybox "od")))
+          (and busybox
+               (tramp-send-command-and-check
+                vec (concat command " -A n </dev/null"))
+               command)))))
+
 (defun tramp-get-env-with-u-option (vec)
   "Check, whether the remote `env' command supports the -u option."
   (with-tramp-connection-property vec "env-u-option"
diff --git a/lisp/net/tramp-smb.el b/lisp/net/tramp-smb.el
index bf77ab9dee8..902fcf4b6e3 100644
--- a/lisp/net/tramp-smb.el
+++ b/lisp/net/tramp-smb.el
@@ -75,12 +75,23 @@
 
 ;;;###tramp-autoload
 (defcustom tramp-smb-conf "/dev/null"
-  "Path of the smb.conf file.
-If it is nil, no smb.conf will be added to the `tramp-smb-program'
+  "Path of the \"smb.conf\" file.
+If it is nil, no \"smb.conf\" will be added to the `tramp-smb-program'
 call, letting the SMB client use the default one."
   :group 'tramp
   :type '(choice (const nil) (file :must-match t)))
 
+;;;###tramp-autoload
+(defcustom tramp-smb-options nil
+  "List of additional options.
+They are added to the `tramp-smb-program' call via \"--option '...'\".
+
+For example, if the deprecated SMB1 protocol shall be used, add to
+this variable (\"client min protocol=NT1\") ."
+  :group 'tramp
+  :type '(repeat string)
+  :version "27.2")
+
 (defvar tramp-smb-version nil
   "Version string of the SMB client.")
 
@@ -135,6 +146,7 @@ call, letting the SMB client use the default one."
          "NT_STATUS_HOST_UNREACHABLE"
          "NT_STATUS_IMAGE_ALREADY_LOADED"
          "NT_STATUS_INVALID_LEVEL"
+         "NT_STATUS_INVALID_PARAMETER"
          "NT_STATUS_INVALID_PARAMETER_MIX"
          "NT_STATUS_IO_TIMEOUT"
          "NT_STATUS_LOGON_FAILURE"
@@ -461,7 +473,8 @@ pass to the OPERATION."
                                (expand-file-name
                                 tramp-temp-name-prefix
                                 (tramp-compat-temporary-file-directory))))
-                   (args      (list (concat "//" host "/" share) "-E")))
+                   (args      (list (concat "//" host "/" share) "-E"))
+                   (options   tramp-smb-options))
 
               (if (not (zerop (length user)))
                   (setq args (append args (list "-U" user)))
@@ -471,6 +484,10 @@ pass to the OPERATION."
               (when port   (setq args (append args (list "-p" port))))
               (when tramp-smb-conf
                 (setq args (append args (list "-s" tramp-smb-conf))))
+              (while options
+                (setq args
+                      (append args `("--option" ,(format "%s" (car options))))
+                      options (cdr options)))
               (setq args
                     (if t1
                         ;; Source is remote.
@@ -760,7 +777,8 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
           (let* ((share     (tramp-smb-get-share v))
                  (localname (replace-regexp-in-string
                              "\\\\" "/" (tramp-smb-get-localname v)))
-                 (args      (list (concat "//" host "/" share) "-E")))
+                 (args      (list (concat "//" host "/" share) "-E"))
+                 (options   tramp-smb-options))
 
             (if (not (zerop (length user)))
                 (setq args (append args (list "-U" user)))
@@ -770,6 +788,10 @@ PRESERVE-UID-GID and PRESERVE-EXTENDED-ATTRIBUTES are completely ignored."
             (when port   (setq args (append args (list "-p" port))))
             (when tramp-smb-conf
               (setq args (append args (list "-s" tramp-smb-conf))))
+            (while options
+              (setq args
+                    (append args `("--option" ,(format "%s" (car options))))
+                    options (cdr options)))
             (setq
              args
              (append args (list (tramp-unquote-shell-quote-argument localname)
@@ -1188,9 +1210,7 @@ component is used as the target of the symlink."
       (let ((non-essential t))
         (when (and (tramp-tramp-file-p target)
                    (tramp-file-name-equal-p v (tramp-dissect-file-name target)))
-          (setq target
-                (tramp-file-name-localname
-                 (tramp-dissect-file-name (expand-file-name target))))))
+          (setq target (tramp-file-local-name (expand-file-name target)))))
 
       ;; If TARGET is still remote, quote it.
       (if (tramp-tramp-file-p target)
@@ -1244,7 +1264,7 @@ component is used as the target of the symlink."
         (setq infile (expand-file-name infile))
         (if (tramp-equal-remote default-directory infile)
             ;; INFILE is on the same remote host.
-            (setq input (with-parsed-tramp-file-name infile nil localname))
+            (setq input (tramp-file-local-name infile))
           ;; INFILE must be copied to remote host.
           (setq input (tramp-make-tramp-temp-file v)
                 tmpinput (tramp-make-tramp-file-name v input))
@@ -1414,7 +1434,8 @@ component is used as the target of the symlink."
                            "\\\\" "/" (tramp-smb-get-localname v)))
                (args      (list (concat "//" host "/" share) "-E" "-S"
                                 (replace-regexp-in-string
-                                 "\n" "," acl-string))))
+                                 "\n" "," acl-string)))
+               (options   tramp-smb-options))
 
           (if (not (zerop (length user)))
               (setq args (append args (list "-U" user)))
@@ -1424,6 +1445,10 @@ component is used as the target of the symlink."
           (when port   (setq args (append args (list "-p" port))))
           (when tramp-smb-conf
             (setq args (append args (list "-s" tramp-smb-conf))))
+          (while options
+            (setq args
+                  (append args `("--option" ,(format "%s" (car options))))
+                  options (cdr options)))
           (setq
            args
            (append args (list (tramp-unquote-shell-quote-argument localname)
@@ -1468,7 +1493,7 @@ component is used as the target of the symlink."
             (tramp-flush-connection-property v "process-name")
             (tramp-flush-connection-property v "process-buffer")))))))
 
-(defun tramp-smb-handle-set-file-modes (filename mode)
+(defun tramp-smb-handle-set-file-modes (filename mode &optional _flag)
   "Like `set-file-modes' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (when (tramp-smb-get-cifs-capabilities v)
@@ -1557,9 +1582,6 @@ errors for shares like \"C$/\", which are common in Microsoft Windows."
                      (format "File %s exists; overwrite anyway? " filename)))))
       (tramp-error v 'file-already-exists filename))
 
-    ;; We must also flush the cache of the directory, because
-    ;; `file-attributes' reads the values from there.
-    (tramp-flush-file-properties v localname)
     (let ((curbuf (current-buffer))
           (tmpfile (tramp-compat-make-temp-file filename)))
       (when (and append (file-exists-p filename))
@@ -1579,6 +1601,10 @@ errors for shares like \"C$/\", which are common in Microsoft Windows."
               (tramp-error v 'file-error "Cannot write `%s'" filename))
           (delete-file tmpfile)))
 
+      ;; We must also flush the cache of the directory, because
+      ;; `file-attributes' reads the values from there.
+      (tramp-flush-file-properties v localname)
+
       (unless (equal curbuf (current-buffer))
         (tramp-error
          v 'file-error
@@ -1949,6 +1975,7 @@ If ARGUMENT is non-nil, use it as argument for
                (host   (tramp-file-name-host vec))
                (domain (tramp-file-name-domain vec))
                (port   (tramp-file-name-port vec))
+               (options tramp-smb-options)
                args)
 
           (cond
@@ -1967,6 +1994,10 @@ If ARGUMENT is non-nil, use it as argument for
           (when port   (setq args (append args (list "-p" port))))
           (when tramp-smb-conf
             (setq args (append args (list "-s" tramp-smb-conf))))
+          (while options
+            (setq args
+                  (append args `("--option" ,(format "%s" (car options))))
+                  options (cdr options)))
           (when argument
             (setq args (append args (list argument))))
 
@@ -2132,7 +2163,5 @@ Removes smb prompt.  Returns nil if an error message has appeared."
 ;;
 ;; * Try to remove the inclusion of dummy "" directory.  Seems to be at
 ;;   several places, especially in `tramp-smb-handle-insert-directory'.
-;;
-;; * Ignore case in file names.
 
 ;;; tramp-smb.el ends here
diff --git a/lisp/net/tramp-sudoedit.el b/lisp/net/tramp-sudoedit.el
index 08188cefde3..4af58618a6a 100644
--- a/lisp/net/tramp-sudoedit.el
+++ b/lisp/net/tramp-sudoedit.el
@@ -265,10 +265,8 @@ absolute file names."
               v 0 (format "%s %s to %s" msg-operation filename newname)
             (unless (tramp-sudoedit-send-command
                      v sudoedit-operation
-                     (tramp-compat-file-name-unquote
-                      (tramp-compat-file-local-name filename))
-                     (tramp-compat-file-name-unquote
-                      (tramp-compat-file-local-name newname)))
+                     (tramp-unquote-file-local-name filename)
+                     (tramp-unquote-file-local-name newname))
               (tramp-error
                v 'file-error
                "Error %s `%s' `%s'" msg-operation filename newname))))
@@ -466,7 +464,7 @@ the result will be a local, non-Tramp, file name."
       (tramp-sudoedit-send-command
        v "test" "-r" (tramp-compat-file-name-unquote localname)))))
 
-(defun tramp-sudoedit-handle-set-file-modes (filename mode)
+(defun tramp-sudoedit-handle-set-file-modes (filename mode &optional _flag)
   "Like `set-file-modes' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (tramp-flush-file-properties v localname)
@@ -524,7 +522,7 @@ the result will be a local, non-Tramp, file name."
                      (string-to-number (match-string 2)))
                   (string-to-number (match-string 3)))))))))
 
-(defun tramp-sudoedit-handle-set-file-times (filename &optional time)
+(defun tramp-sudoedit-handle-set-file-times (filename &optional time _flag)
   "Like `set-file-times' for Tramp files."
   (with-parsed-tramp-file-name filename nil
     (tramp-flush-file-properties v localname)
@@ -615,9 +613,7 @@ component is used as the target of the symlink."
       (let ((non-essential t))
         (when (and (tramp-tramp-file-p target)
                    (tramp-file-name-equal-p v (tramp-dissect-file-name target)))
-          (setq target
-                (tramp-file-name-localname
-                 (tramp-dissect-file-name (expand-file-name target))))))
+          (setq target (tramp-file-local-name (expand-file-name target)))))
 
       ;; If TARGET is still remote, quote it.
       (if (tramp-tramp-file-p target)
@@ -715,8 +711,7 @@ ID-FORMAT valid values are `string' and `integer'."
        (format "%d:%d"
                (or uid (tramp-sudoedit-get-remote-uid v 'integer))
                (or gid (tramp-sudoedit-get-remote-gid v 'integer)))
-       (tramp-compat-file-name-unquote
-        (tramp-compat-file-local-name filename)))))
+       (tramp-unquote-file-local-name filename))))
 
 (defun tramp-sudoedit-handle-write-region
   (start end filename &optional append visit lockname mustbenew)
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index 4f3249d966a..2e6fbe1c767 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -7,7 +7,7 @@
 ;; Maintainer: Michael Albinus <michael.albinus@gmx.de>
 ;; Keywords: comm, processes
 ;; Package: tramp
-;; Version: 2.4.3
+;; Version: 2.4.5-pre
 ;; Package-Requires: ((emacs "24.4"))
 ;; Package-Type: multi
 ;; URL: https://savannah.gnu.org/projects/tramp
@@ -37,7 +37,7 @@
 ;; For more detailed instructions, please see the info file.
 ;;
 ;; Notes:
-;; -----
+;; ------
 ;;
 ;; Also see the todo list at the bottom of this file.
 ;;
@@ -46,6 +46,7 @@
 ;;
 ;; There's a mailing list for this, as well.  Its name is:
 ;;            tramp-devel@gnu.org
+
 ;; You can use the Web to subscribe, under the following URL:
 ;;            https://lists.gnu.org/mailman/listinfo/tramp-devel
 ;;
@@ -1347,6 +1348,11 @@ of `process-file', `start-file-process', or `shell-command'."
            (match-string (nth 4 tramp-file-name-structure) name))
       (tramp-compat-file-local-name name)))
 
+;; The localname can be quoted with "/:".  Extract this.
+(defun tramp-unquote-file-local-name (name)
+  "Return unquoted localname of NAME."
+  (tramp-compat-file-name-unquote (tramp-file-local-name name)))
+
 (defun tramp-find-method (method user host)
   "Return the right method string to use depending on USER and HOST.
 This is METHOD, if non-nil.  Otherwise, do a lookup in
@@ -1592,7 +1598,7 @@ necessary only.  This function will be used in file name completion."
                   tramp-prefix-ipv6-format host tramp-postfix-ipv6-format)
                host)
              tramp-postfix-host-format))
-          (when localname localname)))
+          localname))
 
 (defun tramp-get-buffer (vec &optional dont-create)
   "Get the connection buffer to be used for VEC.
@@ -1648,7 +1654,7 @@ version, the function does nothing."
   "Set connection-local variables in the current buffer.
 If connection-local variables are not supported by this Emacs
 version, the function does nothing."
-  (when (file-remote-p default-directory)
+  (when (tramp-tramp-file-p default-directory)
     ;; `hack-connection-local-variables-apply' exists since Emacs 26.1.
     (tramp-compat-funcall
      'hack-connection-local-variables-apply
@@ -2864,7 +2870,7 @@ User is always nil."
   (let ((default-directory (tramp-compat-temporary-file-directory)))
     (when (file-readable-p filename)
       (with-temp-buffer
-        (insert-file-contents filename)
+        (insert-file-contents-literally filename)
         (goto-char (point-min))
         (cl-loop while (not (eobp)) collect (funcall function))))))
 
@@ -3199,7 +3205,7 @@ User is always nil."
       (copy-file filename tmpfile 'ok-if-already-exists 'keep-time)
       tmpfile)))
 
-(defun tramp-handle-file-modes (filename)
+(defun tramp-handle-file-modes (filename &optional _flag)
   "Like `file-modes' for Tramp files."
   ;; Starting with Emacs 25.1, `when-let' can be used.
   (let ((attrs (file-attributes (or (file-truename filename) filename))))
@@ -3247,7 +3253,7 @@ User is always nil."
                   ;; lower case letters.  This avoids us to create a
                   ;; temporary file.
                   (while (and (string-match-p
-                               "[a-z]" (tramp-compat-file-local-name candidate))
+                               "[a-z]" (tramp-file-local-name candidate))
                               (not (file-exists-p candidate)))
                     (setq candidate
                           (directory-file-name
@@ -3257,8 +3263,7 @@ User is always nil."
                   ;; to Emacs 26+ like `file-name-case-insensitive-p',
                   ;; so there is no compatibility problem calling it.
                   (unless
-                      (string-match-p
-                       "[a-z]" (tramp-compat-file-local-name candidate))
+                      (string-match-p "[a-z]" (tramp-file-local-name candidate))
                     (setq tmpfile
                           (let ((default-directory
                                   (file-name-directory filename)))
@@ -3271,7 +3276,7 @@ User is always nil."
                       (file-exists-p
                        (concat
                         (file-remote-p candidate)
-                        (upcase (tramp-compat-file-local-name candidate))))
+                        (upcase (tramp-file-local-name candidate))))
                     ;; Cleanup.
                     (when tmpfile (delete-file tmpfile)))))))))))
 
@@ -3413,7 +3418,7 @@ User is always nil."
                (tramp-error
                 v1 'file-error
                 "Maximum number (%d) of symlinks exceeded" numchase-limit)))
-           (tramp-compat-file-local-name (directory-file-name result)))))))))
+           (tramp-file-local-name (directory-file-name result)))))))))
 
 (defun tramp-handle-file-writable-p (filename)
   "Like `file-writable-p' for Tramp files."
@@ -3645,10 +3650,16 @@ support symbolic links."
   (let* ((asynchronous (string-match-p "[ \t]*&[ \t]*\\'" command))
          (command (substring command 0 asynchronous))
          current-buffer-p
+         (output-buffer-p output-buffer)
          (output-buffer
           (cond
-           ((bufferp output-buffer) output-buffer)
-           ((stringp output-buffer) (get-buffer-create output-buffer))
+           ((bufferp output-buffer)
+            (setq current-buffer-p (eq (current-buffer) output-buffer))
+            output-buffer)
+           ((stringp output-buffer)
+            (setq current-buffer-p
+                  (eq (buffer-name (current-buffer)) output-buffer))
+            (get-buffer-create output-buffer))
            (output-buffer
             (setq current-buffer-p t)
             (current-buffer))
@@ -3660,13 +3671,19 @@ support symbolic links."
           (cond
            ((bufferp error-buffer) error-buffer)
            ((stringp error-buffer) (get-buffer-create error-buffer))))
+         (error-file
+          (and error-buffer
+               (with-parsed-tramp-file-name default-directory nil
+                 (tramp-make-tramp-file-name
+                  v (tramp-make-tramp-temp-file v)))))
          (bname (buffer-name output-buffer))
          (p (get-buffer-process output-buffer))
+         (dir default-directory)
          buffer)
 
     ;; The following code is taken from `shell-command', slightly
     ;; adapted.  Shouldn't it be factored out?
-    (when p
+    (when (and (integerp asynchronous) p)
       (cond
        ((eq async-shell-command-buffer 'confirm-kill-process)
         ;; If will kill a process, query first.
@@ -3698,22 +3715,25 @@ support symbolic links."
           (rename-uniquely))
         (setq output-buffer (get-buffer-create bname)))))
 
-    (setq buffer (if (and (not asynchronous) error-buffer)
-                     (with-parsed-tramp-file-name default-directory nil
-                       (list output-buffer
-                             (tramp-make-tramp-file-name
-                              v (tramp-make-tramp-temp-file v))))
-                   output-buffer))
-
-    (if current-buffer-p
-        (progn
-          (barf-if-buffer-read-only)
-          (push-mark nil t))
+    (unless output-buffer-p
       (with-current-buffer output-buffer
+        (setq default-directory dir)))
+
+    (setq buffer (if error-file (list output-buffer error-file) output-buffer))
+
+    (with-current-buffer output-buffer
+      (when current-buffer-p
+        (barf-if-buffer-read-only)
+        (push-mark nil t))
+      ;; `shell-command-save-pos-or-erase' has been introduced with
+      ;; Emacs 27.1.
+      (if (fboundp 'shell-command-save-pos-or-erase)
+          (tramp-compat-funcall
+           'shell-command-save-pos-or-erase current-buffer-p)
         (setq buffer-read-only nil)
         (erase-buffer)))
 
-    (if (and (not current-buffer-p) (integerp asynchronous))
+    (if (integerp asynchronous)
         (let ((tramp-remote-process-environment
                ;; `async-shell-command-width' has been introduced with
                ;; Emacs 27.1.
@@ -3726,42 +3746,68 @@ support symbolic links."
               ;; Run the process.
               (setq p (start-file-process-shell-command
                        (buffer-name output-buffer) buffer command))
-            ;; Display output.
-            (with-current-buffer output-buffer
-              (display-buffer output-buffer '(nil (allow-no-window . t)))
-              (setq mode-line-process '(":%s"))
-              (shell-mode)
-              (set-process-sentinel p #'shell-command-sentinel)
-              (set-process-filter p #'comint-output-filter))))
+            ;; Insert error messages if they were separated.
+            (when error-file
+              (with-current-buffer error-buffer
+                (insert-file-contents-literally error-file)))
+            (if (process-live-p p)
+              ;; Display output.
+              (with-current-buffer output-buffer
+                (setq mode-line-process '(":%s"))
+                (unless (eq major-mode 'shell-mode)
+                  (shell-mode))
+                (set-process-filter p #'comint-output-filter)
+                (set-process-sentinel p #'shell-command-sentinel)
+                (when error-file
+                  (add-function
+                   :after (process-sentinel p)
+                   (lambda (_proc _string)
+                     (with-current-buffer error-buffer
+                       (insert-file-contents-literally
+                        error-file nil nil nil 'replace))
+                     (delete-file error-file))))
+                (display-buffer output-buffer '(nil (allow-no-window . t))))
+
+              (when error-file
+                (delete-file error-file)))))
 
       (prog1
           ;; Run the process.
           (process-file-shell-command command nil buffer nil)
         ;; Insert error messages if they were separated.
-        (when (listp buffer)
+        (when error-file
           (with-current-buffer error-buffer
-            (insert-file-contents (cadr buffer)))
-          (delete-file (cadr buffer)))
+            (insert-file-contents-literally error-file))
+          (delete-file error-file))
         (if current-buffer-p
             ;; This is like exchange-point-and-mark, but doesn't
             ;; activate the mark.  It is cleaner to avoid activation,
             ;; even though the command loop would deactivate the mark
             ;; because we inserted text.
-            (goto-char (prog1 (mark t)
-                         (set-marker (mark-marker) (point)
-                                     (current-buffer))))
+            (progn
+              (goto-char (prog1 (mark t)
+                           (set-marker (mark-marker) (point)
+                                       (current-buffer))))
+              ;; `shell-command-set-point-after-cmd' has been
+              ;; introduced with Emacs 27.1.
+              (if (fboundp 'shell-command-set-point-after-cmd)
+                  (tramp-compat-funcall
+                   'shell-command-set-point-after-cmd)))
           ;; There's some output, display it.
           (when (with-current-buffer output-buffer (> (point-max) (point-min)))
             (display-message-or-buffer output-buffer)))))))
 
 (defun tramp-handle-start-file-process (name buffer program &rest args)
-  "Like `start-file-process' for Tramp files."
+  "Like `start-file-process' for Tramp files.
+BUFFER might be a list, in this case STDERR is separated."
   ;; `make-process' knows the `:file-handler' argument since Emacs 27.1 only.
   (tramp-file-name-handler
    'make-process
    :name name
-   :buffer buffer
+   :buffer (if (consp buffer) (car buffer) buffer)
    :command (and program (cons program args))
+   ;; `shell-command' adds an errfile to `buffer'.
+   :stderr (when (consp buffer) (cadr buffer))
    :noquery nil
    :file-handler t))
 
@@ -4044,6 +4090,8 @@ The terminal type can be configured with `tramp-terminal-type'."
 (defun tramp-action-process-alive (proc _vec)
   "Check, whether a process has finished."
   (unless (process-live-p proc)
+    ;; There might be pending output.
+    (while (tramp-accept-process-output proc 0))
     (throw 'tramp-action 'process-died)))
 
 (defun tramp-action-out-of-band (proc vec)
@@ -4362,7 +4410,7 @@ would yield t.  On the other hand, the following check results in nil:
   (tramp-equal-remote \"/sudo::/etc\" \"/su::/etc\")
 
 If both files are local, the function returns t."
-  (or (and (null (file-remote-p file1)) (null (file-remote-p file2)))
+  (or (and (null (tramp-tramp-file-p file1)) (null (tramp-tramp-file-p file2)))
       (and (tramp-tramp-file-p file1) (tramp-tramp-file-p file2)
            (string-equal (file-remote-p file1) (file-remote-p file2)))))
 
@@ -4632,7 +4680,7 @@ This handles also chrooted environments, which are not regarded as local."
            (tramp-make-tramp-file-name
             vec (or (tramp-get-method-parameter vec 'tramp-tmpdir) "/tmp"))))
       (or (and (file-directory-p dir) (file-writable-p dir)
-               (tramp-compat-file-local-name dir))
+               (tramp-file-local-name dir))
           (tramp-error vec 'file-error "Directory %s not accessible" dir))
       dir)))
 
@@ -4655,7 +4703,7 @@ Return the local name of the temporary file."
         (set-file-modes result #o0700)))
 
     ;; Return the local part.
-    (with-parsed-tramp-file-name result nil localname)))
+    (tramp-file-local-name result)))
 
 (defun tramp-delete-temp-file-function ()
   "Remove temporary files related to current buffer."
@@ -4682,7 +4730,7 @@ this file, if that variable is non-nil."
 
   (let ((system-type
          (if (and (stringp tramp-auto-save-directory)
-                  (file-remote-p tramp-auto-save-directory))
+                  (tramp-tramp-file-p tramp-auto-save-directory))
              'not-windows
            system-type))
         (auto-save-file-name-transforms
@@ -4824,7 +4872,12 @@ verbosity of 6."
   "Read a password from user (compat function).
 Consults the auth-source package.
 Invokes `password-read' if available, `read-passwd' else."
-  (let* ((case-fold-search t)
+  (let* (;; If `auth-sources' contains "~/.authinfo.gpg", and
+         ;; `exec-path' contains a relative file name like ".", it
+         ;; could happen that the "gpg" command is not found.  So we
+         ;; adapt `default-directory'.  (Bug#39389, Bug#39489)
+         (default-directory (tramp-compat-temporary-file-directory))
+         (case-fold-search t)
          (key (tramp-make-tramp-file-name
                ;; In tramp-sh.el, we must use "password-vector" due to
                ;; multi-hop.
@@ -4976,10 +5029,12 @@ name of a process or buffer, or nil to default to the current buffer."
           (tramp-error proc 'error "Process %s is not active" proc)
         (tramp-message proc 5 "Interrupt process %s with pid %s" proc pid)
         ;; This is for tramp-sh.el.  Other backends do not support this (yet).
+        ;; Not all "kill" implementations support process groups by
+        ;; negative pid, so we try both variants.
         (tramp-compat-funcall
          'tramp-send-command
          (process-get proc 'vector)
-         (format "kill -2 -%d" pid))
+         (format "(\\kill -2 -%d || \\kill -2 %d) 2>/dev/null" pid pid))
         ;; Wait, until the process has disappeared.  If it doesn't,
         ;; fall back to the default implementation.
         (while (tramp-accept-process-output proc 0))
diff --git a/lisp/net/trampver.el b/lisp/net/trampver.el
index dacdd44102f..4aed8abd9b3 100644
--- a/lisp/net/trampver.el
+++ b/lisp/net/trampver.el
@@ -39,7 +39,7 @@
 (defvar inhibit-message)
 
 ;;;###tramp-autoload
-(defconst tramp-version "2.4.3.27.1"
+(defconst tramp-version "2.4.5-pre"
   "This version of Tramp.")
 
 ;;;###tramp-autoload
@@ -51,6 +51,7 @@
     ;; Suppress message from `emacs-repository-get-branch'.  We must
     ;; also handle out-of-tree builds.
     (let ((inhibit-message t)
+          (debug-on-error nil)
           (dir (or (locate-dominating-file (locate-library "tramp") ".git")
                    source-directory)))
       ;; `emacs-repository-get-branch' has been introduced with Emacs 27.1.
@@ -64,6 +65,7 @@
     ;; Suppress message from `emacs-repository-get-version'.  We must
     ;; also handle out-of-tree builds.
     (let ((inhibit-message t)
+          (debug-on-error nil)
           (dir (or (locate-dominating-file (locate-library "tramp") ".git")
                    source-directory)))
       (and (stringp dir) (file-directory-p dir)
@@ -73,7 +75,7 @@
 ;; Check for Emacs version.
 (let ((x   (if (not (string-lessp emacs-version "24.4"))
       "ok"
-    (format "Tramp 2.4.3.27.1 is not fit for %s"
+    (format "Tramp 2.4.5-pre is not fit for %s"
             (replace-regexp-in-string "\n" "" (emacs-version))))))
   (unless (string-equal "ok" x) (error "%s" x)))
 
diff --git a/test/lisp/net/tramp-tests.el b/test/lisp/net/tramp-tests.el
index 544bdb5c058..9e46d7f538b 100644
--- a/test/lisp/net/tramp-tests.el
+++ b/test/lisp/net/tramp-tests.el
@@ -50,6 +50,7 @@
 (require 'vc-hg)
 
 (declare-function tramp-find-executable "tramp-sh")
+(declare-function tramp-get-remote-gid "tramp-sh")
 (declare-function tramp-get-remote-path "tramp-sh")
 (declare-function tramp-get-remote-perl "tramp-sh")
 (declare-function tramp-get-remote-stat "tramp-sh")
@@ -74,6 +75,9 @@
 (defvar connection-local-profile-alist)
 ;; Needed for Emacs 26.
 (defvar async-shell-command-width)
+;; Needed for Emacs 27.
+(defvar process-file-return-signal-string)
+(defvar shell-command-dont-erase-buffer)
 
 ;; Beautify batch mode.
 (when noninteractive
@@ -2357,7 +2361,14 @@ This checks also `file-name-as-directory', `file-name-directory',
                 (write-region nil nil tmp-name 3))
               (with-temp-buffer
                 (insert-file-contents tmp-name)
-                (should (string-equal (buffer-string) "foobaz"))))
+                (should (string-equal (buffer-string) "foobaz")))
+              (delete-file tmp-name)
+              (with-temp-buffer
+                (insert "foo")
+                (write-region nil nil tmp-name 'append))
+              (with-temp-buffer
+                (insert-file-contents tmp-name)
+                (should (string-equal (buffer-string) "foo"))))
 
             ;; Write string.
             (write-region "foo" nil tmp-name)
@@ -2393,14 +2404,14 @@ This checks also `file-name-as-directory', `file-name-directory',
                         tramp--test-messages))))))))
 
             ;; Do not overwrite if excluded.
-            (cl-letf (((symbol-function 'y-or-n-p) (lambda (_prompt) t))
+            (cl-letf (((symbol-function #'y-or-n-p) (lambda (_prompt) t))
                       ;; Ange-FTP.
                       ((symbol-function 'yes-or-no-p) (lambda (_prompt) t)))
               (write-region "foo" nil tmp-name nil nil nil 'mustbenew))
             ;; `mustbenew' is passed to Tramp since Emacs 26.1.
             (when (tramp--test-emacs26-p)
               (should-error
-               (cl-letf (((symbol-function 'y-or-n-p) 'ignore)
+               (cl-letf (((symbol-function #'y-or-n-p) #'ignore)
                          ;; Ange-FTP.
                          ((symbol-function 'yes-or-no-p) 'ignore))
                  (write-region "foo" nil tmp-name nil nil nil 'mustbenew))
@@ -3115,22 +3126,38 @@ This tests also `access-file', `file-readable-p',
              (file-remote-p tmp-name1)
              (replace-regexp-in-string
               "/" "//" (file-remote-p tmp-name1 'localname))))
+           ;; `file-ownership-preserved-p' is implemented only in tramp-sh.el.
+           (test-file-ownership-preserved-p (tramp--test-sh-p))
            attr)
       (unwind-protect
           (progn
+            ;; A sticky bit could damage the `file-ownership-preserved-p' test.
+            (when
+                (and test-file-ownership-preserved-p
+                     (zerop (logand
+                             #o1000
+                             (file-modes tramp-test-temporary-file-directory))))
+              (write-region "foo" nil tmp-name1)
+              (setq test-file-ownership-preserved-p
+                    (= (tramp-compat-file-attribute-group-id
+                        (file-attributes tmp-name1))
+                       (tramp-get-remote-gid
+                        (tramp-dissect-file-name tmp-name1) 'integer)))
+              (delete-file tmp-name1))
+
             (should-error
              (access-file tmp-name1 "error")
              :type tramp-file-missing)
             ;; `file-ownership-preserved-p' should return t for
-            ;; non-existing files.  It is implemented only in tramp-sh.el.
-            (when (tramp--test-sh-p)
+            ;; non-existing files.
+            (when test-file-ownership-preserved-p
               (should (file-ownership-preserved-p tmp-name1 'group)))
             (write-region "foo" nil tmp-name1)
             (should (file-exists-p tmp-name1))
             (should (file-readable-p tmp-name1))
             (should (file-regular-p tmp-name1))
             (should-not (access-file tmp-name1 "error"))
-            (when (tramp--test-sh-p)
+            (when test-file-ownership-preserved-p
               (should (file-ownership-preserved-p tmp-name1 'group)))
 
             ;; We do not test inodes and device numbers.
@@ -3160,16 +3187,16 @@ This tests also `access-file', `file-readable-p',
             (should (stringp (tramp-compat-file-attribute-group-id attr)))
 
             (tramp--test-ignore-make-symbolic-link-error
-             (should-error
-              (access-file tmp-name2 "error")
-              :type tramp-file-missing)
-              (when (tramp--test-sh-p)
+              (should-error
+               (access-file tmp-name2 "error")
+               :type tramp-file-missing)
+              (when test-file-ownership-preserved-p
                 (should (file-ownership-preserved-p tmp-name2 'group)))
               (make-symbolic-link tmp-name1 tmp-name2)
               (should (file-exists-p tmp-name2))
               (should (file-symlink-p tmp-name2))
               (should-not (access-file tmp-name2 "error"))
-              (when (tramp--test-sh-p)
+              (when test-file-ownership-preserved-p
                 (should (file-ownership-preserved-p tmp-name2 'group)))
               (setq attr (file-attributes tmp-name2))
               (should
@@ -3200,7 +3227,7 @@ This tests also `access-file', `file-readable-p',
                  (tramp-dissect-file-name tmp-name3))))
               (delete-file tmp-name2))
 
-            (when (tramp--test-sh-p)
+            (when test-file-ownership-preserved-p
               (should (file-ownership-preserved-p tmp-name1 'group)))
             (delete-file tmp-name1)
             (make-directory tmp-name1)
@@ -3208,7 +3235,7 @@ This tests also `access-file', `file-readable-p',
             (should (file-readable-p tmp-name1))
             (should-not (file-regular-p tmp-name1))
             (should-not (access-file tmp-name1 ""))
-            (when (tramp--test-sh-p)
+            (when test-file-ownership-preserved-p
               (should (file-ownership-preserved-p tmp-name1 'group)))
             (setq attr (file-attributes tmp-name1))
             (should (eq (tramp-compat-file-attribute-type attr) t)))
@@ -3420,11 +3447,11 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                :type 'file-already-exists))
             (when (tramp--test-expensive-test)
               ;; A number means interactive case.
-              (cl-letf (((symbol-function 'yes-or-no-p) #'ignore))
+              (cl-letf (((symbol-function #'yes-or-no-p) #'ignore))
                 (should-error
                  (make-symbolic-link tmp-name1 tmp-name2 0)
                  :type 'file-already-exists)))
-            (cl-letf (((symbol-function 'yes-or-no-p) (lambda (_prompt) t)))
+            (cl-letf (((symbol-function #'yes-or-no-p) (lambda (_prompt) t)))
               (make-symbolic-link tmp-name1 tmp-name2 0)
               (should
                (string-equal
@@ -3496,11 +3523,11 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
               (add-name-to-file tmp-name1 tmp-name2)
               :type 'file-already-exists)
              ;; A number means interactive case.
-             (cl-letf (((symbol-function 'yes-or-no-p) #'ignore))
+             (cl-letf (((symbol-function #'yes-or-no-p) #'ignore))
                (should-error
                 (add-name-to-file tmp-name1 tmp-name2 0)
                 :type 'file-already-exists))
-             (cl-letf (((symbol-function 'yes-or-no-p) (lambda (_prompt) t)))
+             (cl-letf (((symbol-function #'yes-or-no-p) (lambda (_prompt) t)))
                (add-name-to-file tmp-name1 tmp-name2 0)
                (should (file-regular-p tmp-name2)))
              (add-name-to-file tmp-name1 tmp-name2 'ok-if-already-exists)
@@ -4126,6 +4153,28 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
             (should (zerop (process-file "true")))
             (should-not (zerop (process-file "false")))
             (should-not (zerop (process-file "binary-does-not-exist")))
+            ;; Return exit code.
+            (should (= 42 (process-file
+                           (if (tramp--test-adb-p) "/system/bin/sh" "/bin/sh")
+                           nil nil nil "-c" "exit 42")))
+            ;; Return exit code in case the process is interrupted,
+            ;; and there's no indication for a signal describing string.
+            (let (process-file-return-signal-string)
+              (should
+               (= (+ 128 2)
+                  (process-file
+                   (if (tramp--test-adb-p) "/system/bin/sh" "/bin/sh")
+                   nil nil nil "-c" "kill -2 $$"))))
+            ;; Return string in case the process is interrupted and
+            ;; there's an indication for a signal describing string.
+            (let ((process-file-return-signal-string t))
+              (should
+               (string-match
+                "Interrupt\\|Signal 2"
+                (process-file
+                 (if (tramp--test-adb-p) "/system/bin/sh" "/bin/sh")
+                 nil nil nil "-c" "kill -2 $$"))))
+
             (with-temp-buffer
               (write-region "foo" nil tmp-name)
               (should (file-exists-p tmp-name))
@@ -4181,7 +4230,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
             (setq proc (start-file-process "test1" (current-buffer) "cat"))
             (should (processp proc))
             (should (equal (process-status proc) 'run))
-            (process-send-string proc "foo")
+            (process-send-string proc "foo\n")
             (process-send-eof proc)
             ;; Read output.
             (with-timeout (10 (tramp--test-timeout-handler))
@@ -4224,7 +4273,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
             (set-process-filter
              proc
              (lambda (p s) (with-current-buffer (process-buffer p) (insert s))))
-            (process-send-string proc "foo")
+            (process-send-string proc "foo\n")
             (process-send-eof proc)
             ;; Read output.
             (with-timeout (10 (tramp--test-timeout-handler))
@@ -4248,7 +4297,8 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
 
   (dolist (quoted (if (tramp--test-expensive-test) '(nil t) '(nil)))
     (let ((default-directory tramp-test-temporary-file-directory)
-          (tmp-name (tramp--test-make-temp-name nil quoted))
+          (tmp-name1 (tramp--test-make-temp-name nil quoted))
+          (tmp-name2 (tramp--test-make-temp-name 'local quoted))
           kill-buffer-query-functions proc)
       (with-no-warnings (should-not (make-process)))
 
@@ -4262,7 +4312,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                      :file-handler t)))
             (should (processp proc))
             (should (equal (process-status proc) 'run))
-            (process-send-string proc "foo")
+            (process-send-string proc "foo\n")
             (process-send-eof proc)
             ;; Read output.
             (with-timeout (10 (tramp--test-timeout-handler))
@@ -4278,13 +4328,13 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
       ;; Simple process using a file.
       (unwind-protect
           (with-temp-buffer
-            (write-region "foo" nil tmp-name)
-            (should (file-exists-p tmp-name))
+            (write-region "foo" nil tmp-name1)
+            (should (file-exists-p tmp-name1))
             (setq proc
                   (with-no-warnings
                     (make-process
                      :name "test2" :buffer (current-buffer)
-                     :command `("cat" ,(file-name-nondirectory tmp-name))
+                     :command `("cat" ,(file-name-nondirectory tmp-name1))
                      :file-handler t)))
             (should (processp proc))
             ;; Read output.
@@ -4296,7 +4346,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
         ;; Cleanup.
         (ignore-errors
           (delete-process proc)
-          (delete-file tmp-name)))
+          (delete-file tmp-name1)))
 
       ;; Process filter.
       (unwind-protect
@@ -4311,7 +4361,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                      :file-handler t)))
             (should (processp proc))
             (should (equal (process-status proc) 'run))
-            (process-send-string proc "foo")
+            (process-send-string proc "foo\n")
             (process-send-eof proc)
             ;; Read output.
             (with-timeout (10 (tramp--test-timeout-handler))
@@ -4337,7 +4387,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                      :file-handler t)))
             (should (processp proc))
             (should (equal (process-status proc) 'run))
-            (process-send-string proc "foo")
+            (process-send-string proc "foo\n")
             (process-send-eof proc)
             (delete-process proc)
             ;; Read output.
@@ -4345,36 +4395,67 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
               (while (accept-process-output proc 0 nil t)))
             ;; We cannot use `string-equal', because tramp-adb.el
             ;; echoes also the sent string.  And a remote macOS sends
-            ;; a slightly modified string.
-            (should (string-match "killed.*\n\\'" (buffer-string))))
+            ;; a slightly modified string.  On MS Windows,
+            ;; `delete-process' sends an unknown signal.
+            (should
+             (string-match
+              (if (eq system-type 'windows-nt)
+                  "unknown signal\n\\'" "killed.*\n\\'")
+              (buffer-string))))
 
         ;; Cleanup.
         (ignore-errors (delete-process proc)))
 
-      ;; Process with stderr.  tramp-adb.el doesn't support it (yet).
-      (unless (tramp--test-adb-p)
-        (let ((stderr (generate-new-buffer "*stderr*")))
-          (unwind-protect
+      ;; Process with stderr buffer.
+      (let ((stderr (generate-new-buffer "*stderr*")))
+        (unwind-protect
+            (with-temp-buffer
+              (setq proc
+                    (with-no-warnings
+                      (make-process
+                       :name "test5" :buffer (current-buffer)
+                       :command '("cat" "/does-not-exist")
+                       :stderr stderr
+                       :file-handler t)))
+              (should (processp proc))
+              ;; Read stderr.
+              (with-timeout (10 (tramp--test-timeout-handler))
+                (while (accept-process-output proc 0 nil t)))
+              (delete-process proc)
+              (with-current-buffer stderr
+                (should
+                 (string-match
+                  "cat:.* No such file or directory" (buffer-string)))))
+
+          ;; Cleanup.
+          (ignore-errors (delete-process proc))
+          (ignore-errors (kill-buffer stderr))))
+
+      ;; Process with stderr file.
+      (dolist (tmpfile `(,tmp-name1 ,tmp-name2))
+        (unwind-protect
+            (with-temp-buffer
+              (setq proc
+                    (with-no-warnings
+                      (make-process
+                       :name "test6" :buffer (current-buffer)
+                       :command '("cat" "/does-not-exist")
+                       :stderr tmpfile
+                       :file-handler t)))
+              (should (processp proc))
+              ;; Read stderr.
+              (with-timeout (10 (tramp--test-timeout-handler))
+                (while (accept-process-output proc nil nil t)))
+              (delete-process proc)
               (with-temp-buffer
-                (setq proc
-                      (with-no-warnings
-                        (make-process
-                         :name "test5" :buffer (current-buffer)
-                         :command '("cat" "/")
-                         :stderr stderr
-                         :file-handler t)))
-                (should (processp proc))
-                ;; Read stderr.
-                (with-current-buffer stderr
-                  (with-timeout (10 (tramp--test-timeout-handler))
-                    (while (= (point-min) (point-max))
-                      (while (accept-process-output proc 0 nil t))))
-                  (should
-                   (string-match "^cat:.* Is a directory" (buffer-string)))))
+                (insert-file-contents tmpfile)
+                (should
+                 (string-match
+                  "cat:.* No such file or directory" (buffer-string)))))
 
-            ;; Cleanup.
-            (ignore-errors (delete-process proc))
-            (ignore-errors (kill-buffer stderr))))))))
+          ;; Cleanup.
+          (ignore-errors (delete-process proc))
+          (ignore-errors (delete-file tmpfile)))))))
 
 (ert-deftest tramp-test31-interrupt-process ()
   "Check `interrupt-process'."
@@ -4388,10 +4469,13 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
   ;; order to establish the connection prior running an asynchronous
   ;; process.
   (let ((default-directory (file-truename tramp-test-temporary-file-directory))
+        (delete-exited-processes t)
         kill-buffer-query-functions proc)
     (unwind-protect
         (with-temp-buffer
-          (setq proc (start-file-process "test" (current-buffer) "sleep" "10"))
+          (setq proc (start-file-process-shell-command
+                      "test" (current-buffer)
+                      "trap 'echo boom; exit 1' 2; sleep 100"))
           (should (processp proc))
           (should (process-live-p proc))
           (should (equal (process-status proc) 'run))
@@ -4399,7 +4483,8 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
           (should (interrupt-process proc))
           ;; Let the process accept the interrupt.
           (with-timeout (10 (tramp--test-timeout-handler))
-            (while (accept-process-output proc nil nil 0)))
+            (while (process-live-p proc)
+              (while (accept-process-output proc 0 nil t))))
           (should-not (process-live-p proc))
           ;; An interrupted process cannot be interrupted, again.
           (should-error
@@ -4409,14 +4494,24 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
       ;; Cleanup.
       (ignore-errors (delete-process proc)))))
 
+(defun tramp--test-async-shell-command
+    (command output-buffer &optional error-buffer input)
+  "Like `async-shell-command', reading the output.
+INPUT, if non-nil, is a string sent to the process."
+  (async-shell-command command output-buffer error-buffer)
+  (let ((proc (get-buffer-process output-buffer))
+        (delete-exited-processes t))
+    (when (stringp input)
+      (process-send-string proc input))
+    (with-timeout
+        ((if (getenv "EMACS_EMBA_CI") 30 10) (tramp--test-timeout-handler))
+      (while (or (accept-process-output proc nil nil t) (process-live-p proc))))
+    (accept-process-output proc nil nil t)))
+
 (defun tramp--test-shell-command-to-string-asynchronously (command)
   "Like `shell-command-to-string', but for asynchronous processes."
   (with-temp-buffer
-    (async-shell-command command (current-buffer))
-    (with-timeout
-        ((if (getenv "EMACS_EMBA_CI") 30 10) (tramp--test-timeout-handler))
-      (while (accept-process-output
-              (get-buffer-process (current-buffer)) nil nil t)))
+    (tramp--test-async-shell-command command (current-buffer))
     (buffer-substring-no-properties (point-min) (point-max))))
 
 (ert-deftest tramp-test32-shell-command ()
@@ -4435,111 +4530,294 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
           (inhibit-message t)
           kill-buffer-query-functions)
 
-      ;; Test ordinary `shell-command'.
-      (unwind-protect
-          (with-temp-buffer
-            (write-region "foo" nil tmp-name)
-            (should (file-exists-p tmp-name))
-            (shell-command
-             (format "ls %s" (file-name-nondirectory tmp-name))
-             (current-buffer))
-            ;; `ls' could produce colorized output.
-            (goto-char (point-min))
-            (while
-                (re-search-forward tramp-display-escape-sequence-regexp nil t)
-              (replace-match "" nil nil))
-            (should
-             (string-equal
-              (format "%s\n" (file-name-nondirectory tmp-name))
-              (buffer-string))))
+      (dolist (this-shell-command
+               '(;; Synchronously.
+                 shell-command
+                 ;; Asynchronously.
+                 tramp--test-async-shell-command))
 
-        ;; Cleanup.
-        (ignore-errors (delete-file tmp-name)))
-
-      ;; Test `shell-command' with error buffer.
-      (let ((stderr (generate-new-buffer "*stderr*")))
+        ;; Test ordinary `{async-}shell-command'.
         (unwind-protect
             (with-temp-buffer
-              (shell-command "error" (current-buffer) stderr)
-              (should (= (point-min) (point-max)))
+              (write-region "foo" nil tmp-name)
+              (should (file-exists-p tmp-name))
+              (funcall
+               this-shell-command
+               (format "ls %s" (file-name-nondirectory tmp-name))
+               (current-buffer))
+              ;; `ls' could produce colorized output.
+              (goto-char (point-min))
+              (while
+                  (re-search-forward tramp-display-escape-sequence-regexp nil t)
+                (replace-match "" nil nil))
               (should
-               (string-match
-                "error:.+not found"
-                (with-current-buffer stderr (buffer-string)))))
+               (string-equal
+                (format "%s\n" (file-name-nondirectory tmp-name))
+                (buffer-string))))
 
           ;; Cleanup.
-          (ignore-errors (kill-buffer stderr))))
+          (ignore-errors (delete-file tmp-name)))
 
-      ;; Test ordinary `async-shell-command'.
+        ;; Test `{async-}shell-command' with error buffer.
+        (let ((stderr (generate-new-buffer "*stderr*")))
+          (unwind-protect
+              (with-temp-buffer
+                (funcall
+                 this-shell-command
+                 "echo foo >&2; echo bar" (current-buffer) stderr)
+                (should (string-equal "bar\n" (buffer-string)))
+                ;; Check stderr.
+                (with-current-buffer stderr
+                  (should (string-equal "foo\n" (buffer-string)))))
+
+            ;; Cleanup.
+            (ignore-errors (kill-buffer stderr)))))
+
+      ;; Test sending string to `async-shell-command'.
       (unwind-protect
           (with-temp-buffer
             (write-region "foo" nil tmp-name)
             (should (file-exists-p tmp-name))
-            (async-shell-command
-             (format "ls %s" (file-name-nondirectory tmp-name))
-             (current-buffer))
-            ;; Read output.
-            (with-timeout (10 (tramp--test-timeout-handler))
-              (while (accept-process-output
-                      (get-buffer-process (current-buffer)) nil nil t)))
-            ;; `ls' could produce colorized output.
-            (goto-char (point-min))
-            (while
-                (re-search-forward tramp-display-escape-sequence-regexp nil t)
-              (replace-match "" nil nil))
+            (tramp--test-async-shell-command
+             "read line; ls $line" (current-buffer) nil
+             ;; String to be sent.
+             (format "%s\n" (file-name-nondirectory tmp-name)))
             (should
              (string-equal
-              (format "%s\n" (file-name-nondirectory tmp-name))
+              ;; tramp-adb.el echoes, so we must add the string.
+              (if (tramp--test-adb-p)
+                  (format
+                   "%s\n%s\n"
+                   (file-name-nondirectory tmp-name)
+                   (file-name-nondirectory tmp-name))
+                (format "%s\n" (file-name-nondirectory tmp-name)))
               (buffer-string))))
 
         ;; Cleanup.
-        (ignore-errors (delete-file tmp-name)))
+        (ignore-errors (delete-file tmp-name)))))
 
-      ;; Test sending string to `async-shell-command'.
+  ;; Test `async-shell-command-width'.  It exists since Emacs 26.1,
+  ;; but seems to work since Emacs 27.1 only.
+  (when (and (tramp--test-sh-p) (tramp--test-emacs27-p))
+    (let* ((async-shell-command-width 1024)
+           (default-directory tramp-test-temporary-file-directory)
+           (cols (ignore-errors
+                   (read (tramp--test-shell-command-to-string-asynchronously
+                          "tput cols")))))
+      (when (natnump cols)
+        (should (= cols async-shell-command-width))))))
+
+;; This test is inspired by Bug#39067.
+(ert-deftest tramp-test32-shell-command-dont-erase-buffer ()
+  "Check `shell-command-dont-erase-buffer'."
+  :tags '(:expensive-test)
+  (skip-unless (tramp--test-enabled))
+  (skip-unless (or (tramp--test-adb-p) (tramp--test-sh-p)))
+  ;; Prior Emacs 27, `shell-command-dont-erase-buffer' wasn't working properly.
+  (skip-unless (tramp--test-emacs27-p))
+
+  ;; We check both the local and remote case, in order to guarantee
+  ;; that they behave similar.
+  (dolist (default-directory
+            `(,temporary-file-directory ,tramp-test-temporary-file-directory))
+    (let ((buffer (generate-new-buffer "foo"))
+          ;; Suppress nasty messages.
+          (inhibit-message t)
+          point kill-buffer-query-functions)
       (unwind-protect
-          (with-temp-buffer
-            (write-region "foo" nil tmp-name)
-            (should (file-exists-p tmp-name))
-            (async-shell-command "read line; ls $line" (current-buffer))
-            (process-send-string
-             (get-buffer-process (current-buffer))
-             (format "%s\n" (file-name-nondirectory tmp-name)))
-            ;; Read output.
-            (with-timeout (10 (tramp--test-timeout-handler))
-              (while (accept-process-output
-                      (get-buffer-process (current-buffer)) nil nil t)))
-            ;; `ls' could produce colorized output.
-            (goto-char (point-min))
-            (while
-                (re-search-forward tramp-display-escape-sequence-regexp nil t)
-              (replace-match "" nil nil))
-            ;; We cannot use `string-equal', because tramp-adb.el
-            ;; echoes also the sent string.
-            (should
-             (string-match
-              (format "\\`%s" (regexp-quote (file-name-nondirectory tmp-name)))
-              (buffer-string))))
+          (progn
+            ;; Don't erase if buffer is the current one.  Point is not moved.
+            (let (shell-command-dont-erase-buffer)
+              (with-temp-buffer
+                (insert "bar")
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (point-max)))
+                (shell-command "echo baz" (current-buffer))
+                (should (string-equal "barbaz\n" (buffer-string)))
+                (should (= point (point)))
+                (should-not (= (point) (point-max)))))
+
+            ;; Erase if the buffer is not current one.  Point is not moved.
+            (let (shell-command-dont-erase-buffer)
+              (with-current-buffer buffer
+                (erase-buffer)
+                (insert "bar")
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (point-max)))
+                (with-temp-buffer
+                  (shell-command "echo baz" buffer))
+                (should (string-equal "baz\n" (buffer-string)))
+                (should (= point (point)))
+                (should-not (= (point) (point-max)))))
+
+            ;; Erase if buffer is the current one, but
+            ;; `shell-command-dont-erase-buffer' is set to `erase'.
+            ;; There is no point to check point.
+            (let ((shell-command-dont-erase-buffer 'erase))
+              (with-temp-buffer
+                (insert "bar")
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (point-max)))
+                (shell-command "echo baz" (current-buffer))
+                (should (string-equal "baz\n" (buffer-string)))
+                ;; In the local case, point is not moved after the
+                ;; inserted text.
+                (should (= (point)
+                           (if (file-remote-p default-directory)
+                               (point-max) (point-min))))))
+
+            ;; Don't erase if the buffer is the current one and
+            ;; `shell-command-dont-erase-buffer' is set to
+            ;; `beg-last-out'.  Check point.
+            (let ((shell-command-dont-erase-buffer 'beg-last-out))
+              (with-temp-buffer
+                (insert "bar")
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (point-max)))
+                (shell-command "echo baz" (current-buffer))
+                (should (string-equal "barbaz\n" (buffer-string)))
+                ;; There is still an error in Tramp.
+                (unless (file-remote-p default-directory)
+                  (should (= point (point)))
+                  (should-not (= (point) (point-max))))))
+
+            ;; Don't erase if the buffer is not the current one and
+            ;; `shell-command-dont-erase-buffer' is set to
+            ;; `beg-last-out'.  Check point.
+            (let ((shell-command-dont-erase-buffer 'beg-last-out))
+              (with-current-buffer buffer
+                (erase-buffer)
+                (insert "bar")
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (point-max)))
+                (with-temp-buffer
+                  (shell-command "echo baz" buffer))
+                (should (string-equal "barbaz\n" (buffer-string)))
+                ;; There is still an error in Tramp.
+                (unless (file-remote-p default-directory)
+                  (should (= point (point)))
+                  (should-not (= (point) (point-max))))))
+
+            ;; Don't erase if the buffer is the current one and
+            ;; `shell-command-dont-erase-buffer' is set to
+            ;; `end-last-out'.  Check point.
+            (let ((shell-command-dont-erase-buffer 'end-last-out))
+              (with-temp-buffer
+                (insert "bar")
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (point-max)))
+                (shell-command "echo baz" (current-buffer))
+                (should (string-equal "barbaz\n" (buffer-string)))
+                ;; This does not work as expected in the local case.
+                ;; Therefore, we negate the test for the time being.
+                (should-not
+                 (funcall (if (file-remote-p default-directory) #'identity #'not)
+                          (= point (point))))
+                (should
+                 (funcall (if (file-remote-p default-directory) #'identity #'not)
+                          (= (point) (point-max))))))
+
+            ;; Don't erase if the buffer is not the current one and
+            ;; `shell-command-dont-erase-buffer' is set to
+            ;; `end-last-out'.  Check point.
+            (let ((shell-command-dont-erase-buffer 'end-last-out))
+              (with-current-buffer buffer
+                (erase-buffer)
+                (insert "bar")
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (point-max)))
+                (with-temp-buffer
+                  (shell-command "echo baz" buffer))
+                (should (string-equal "barbaz\n" (buffer-string)))
+                ;; There is still an error in Tramp.
+                (unless (file-remote-p default-directory)
+                  (should-not (= point (point)))
+                  (should (= (point) (point-max))))))
+
+            ;; Don't erase if the buffer is the current one and
+            ;; `shell-command-dont-erase-buffer' is set to
+            ;; `save-point'.  Check point.
+            (let ((shell-command-dont-erase-buffer 'save-point))
+              (with-temp-buffer
+                (insert "bar")
+                (goto-char (1- (point-max)))
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (1- (point-max))))
+                (shell-command "echo baz" (current-buffer))
+                (should (string-equal "babaz\nr" (buffer-string)))
+                ;; There is still an error in Tramp.
+                (unless (file-remote-p default-directory)
+                  (should (= point (point)))
+                  (should-not (= (point) (point-max))))))
+
+            ;; Don't erase if the buffer is not the current one and
+            ;; `shell-command-dont-erase-buffer' is set to
+            ;; `save-point'.  Check point.
+            (let ((shell-command-dont-erase-buffer 'save-point))
+              (with-current-buffer buffer
+                (erase-buffer)
+                (insert "bar")
+                (goto-char (1- (point-max)))
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (1- (point-max))))
+                (with-temp-buffer
+                  (shell-command "echo baz" buffer))
+                ;; This does not work as expected.  Therefore, we
+                ;; use the "wrong" string.
+                (should (string-equal "barbaz\n" (buffer-string)))
+                ;; There is still an error in Tramp.
+                (unless (file-remote-p default-directory)
+                  (should (= point (point)))
+                  (should-not (= (point) (point-max))))))
+
+            ;; Don't erase if the buffer is the current one and
+            ;; `shell-command-dont-erase-buffer' is set to a random
+            ;; value.  Check point.
+            (let ((shell-command-dont-erase-buffer 'random))
+              (with-temp-buffer
+                (insert "bar")
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (point-max)))
+                (shell-command "echo baz" (current-buffer))
+                (should (string-equal "barbaz\n" (buffer-string)))
+                ;; This does not work as expected in the local case.
+                ;; Therefore, we negate the test for the time being.
+                (should-not
+                 (funcall (if (file-remote-p default-directory) #'identity #'not)
+                          (= point (point))))
+                (should
+                 (funcall (if (file-remote-p default-directory) #'identity #'not)
+                          (= (point) (point-max))))))
+
+            ;; Don't erase if the buffer is not the current one and
+            ;; `shell-command-dont-erase-buffer' is set to a random
+            ;; value.  Check point.
+            (let ((shell-command-dont-erase-buffer 'random))
+              (with-current-buffer buffer
+                (erase-buffer)
+                (insert "bar")
+                (setq point (point))
+                (should (string-equal "bar" (buffer-string)))
+                (should (= (point) (point-max)))
+                (with-temp-buffer
+                  (shell-command "echo baz" buffer))
+                (should (string-equal "barbaz\n" (buffer-string)))
+                ;; There is still an error in Tramp.
+                (unless (file-remote-p default-directory)
+                  (should-not (= point (point)))
+                  (should (= (point) (point-max)))))))
 
         ;; Cleanup.
-        (ignore-errors (delete-file tmp-name)))
-
-      ;; Test `async-shell-command-width'.  Since Emacs 27.1.
-      (when (ignore-errors
-              (and (boundp 'async-shell-command-width)
-                   (zerop (call-process "tput" nil nil nil "cols"))
-                   (zerop (process-file "tput" nil nil nil "cols"))))
-        (let (async-shell-command-width)
-          (should
-           (string-equal
-            (format "%s\n" (car (process-lines "tput" "cols")))
-            (tramp--test-shell-command-to-string-asynchronously
-             "tput cols")))
-          (setq async-shell-command-width 1024)
-          (should
-           (string-equal
-            "1024\n"
-            (tramp--test-shell-command-to-string-asynchronously
-             "tput cols"))))))))
+        (ignore-errors (kill-buffer buffer))))))
 
 ;; This test is inspired by Bug#23952.
 (ert-deftest tramp-test33-environment-variables ()
@@ -5753,7 +6031,7 @@ Use the `ls' command."
   ;; Since Emacs 27.1.
   (skip-unless (fboundp 'file-system-info))
 
-  ;; `file-system-info' exists since Emacs 27.  We don't want to see
+  ;; `file-system-info' exists since Emacs 27.1.  We don't want to see
   ;; compiler warnings for older Emacsen.
   (let ((fsi (with-no-warnings
                (file-system-info tramp-test-temporary-file-directory))))
@@ -6191,8 +6469,6 @@ If INTERACTIVE is non-nil, the tests are run interactively."
 ;; * Fix `tramp-test06-directory-file-name' for `ftp'.
 ;; * Investigate, why `tramp-test11-copy-file' and `tramp-test12-rename-file'
 ;;   do not work properly for `nextcloud'.
-;; * Fix `tramp-test29-start-file-process' and
-;;   `tramp-test30-make-process' on MS Windows (`process-send-eof'?).
 ;; * Implement `tramp-test31-interrupt-process' for `adb'.
 ;; * Fix Bug#16928 in `tramp-test43-asynchronous-requests'.  A remote
 ;;   file name operation cannot run in the timer.  Remove `:unstable' tag?